Data from the

NATIONAL VITAL STATISTICS SYSTEM

FactorsAssociatedWith

low Birth Weight

UnitedStates,1976

An analytic study of demographic, socioeconomic, &d health factors associated with Iow birth weight and a review of recent trends

in low birth weight incidence, based on data reported on birth certificates.

DHEW Publication No. (PHS) 80-1915

U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE

Public Health Service

Office of Health Research, Statistics, and Technology

National Center for Health Statistics

Hyattsville, Md. April 1980

Series 21

Number 37
Library of Congress Cataloging in Publication Data

United States. National Center for Health Statistics.

Factors associated with low birth weight, United States, 1976.

(Vital and health statistics: Series 21, Data from the National Vital Statistics Systcm;

no. 37) (DIIEW publication; no. (PI IS) 80-1915)

Includes bibliogmphical rcfcrcnccs.

Supt. of Dots. no.: HE 20.6209:21/37

1. Birth weight, Low-United Statcs~Statistics. 2. Childbirth-United States–Statistics.

I. Title. 11. Series: United States. National Center for IIcalth Statistics. Vital and health

statistics: Series 21, Data from the National Vital Statistics Systcm; no. 37. 111. Series.

United Stntcs. Dept. of 1Icalth, Education, and Welfare. 111I]{\\r pUljliciltiOn; no. (PI 1S)

80-1915.

11A211.A3 no. 37 [RJ60.U51 312’.1’73s 1312’.6] 79-607127

ISI]N 0-8406 -0181-6
NATIONAL CENTER FOR HEALTH STATISTICS

DOROTHY P. RICE, Director

ROBERT A. ISRAEL, Deputy Director

. JACOB J. FELDMAN, Ph.D., Associate Director for Analysis

GAIL F. FISHER, Ph.D., Associate Director for the Cooperative Health Statistics System

ROBERT A. ISIUEL, Acting Associate Director for Data Systems

ROBERT M. THORNER, SC.D.,Assoctite Director for Zntemationa/ Studies

ROBERT C. HUBER, AssocrizteDirector for Management

MONROE G. SIRKEN, Ph.D., Associate Director for Mathematical Statistics

PETER L. HURLEY, Assm&te Director for Operations

JAMES M.ROBEY, Ph.D., Associate Director forProgmm Development

GEORGE A. SCHNACK, Acting Associate Director for Research

ALICE HAYWOOD,Information Officer

DIVISION OF VITAL STATISTICS

JOHN E. PATTERSON, Director

ALICE M. HETZEL, Depu~ Director

ROBERT L. HEUSER, M.A., C’hiefjNataliO Statistics Branch

JOSEPH D. FARRELL, Chief Progmmming Branch

MABEL G. SMITH, Chie&Statistical Resources f?mnch

Vital and Health Statistics-Series 21-No. 37

DHEW Publication No. (PHS) 80-1915

Library of CongressChtalog CiatdNumber 79-607127
.,.

CONTENTS

Introduction ............................................... ......................................................... .................................

Summary of Pnncipai Findings .................... ... .... ..................... ..........................................................

Recent Trends in the Incidence of Low Birth Weight ..........................................................................".

Age and Birth Order Changes ..... ......................................................................................................

Weight Distribution Changes . .................................. ............... .......................... .............................

Period of Gestation ............................................................. ..................................................................

Demographic CorrcJates .............." .................................................. ..................... ..." ...................e ......

Race and Mother’s NativiW .................................................. ............................................................

Age of Mother and Bii Order ........................................ ................................................................

Plurality of Birth ..................................... .........................................................................................

Social Factors .........................................................................................................................................

Marital Status ................................................ .................... ..............................................................

Educational Attainment of Mother .......................... ..................... . ................................................

Pregnancy History ..................................................................... ...................................... .....................

Premtal Care .................................................. ..................... .......................... .................................

Outcome of L+ Pregnancy and Birth Intend ............... . ...............................................................

Geographic Variations .......................................................... ............................ ....................................

References .................................................... ... ............... .................................................. ..................

List of Detailed Tables ....................................................................... ....................................... ...........

Appendixes

I. ‘lkduicd Notes .............................................................................................................. .........

11. Definition of Terms ....... ........................................................................w................................

111. Direct Standardization of Percent Low Birth Weight by Marital Statusand Month of Preg1.

2.

3.

4.

5.

A.

nancy Prenatal .Care Began ........................................................................................................

LIST OF TEXT FIGURES

Percent of infants of low birth weight by race: United States, 1950-76 .................................. ......

Actual and adjusted percent of infants of low birth weight, by color: United States, 1966-76 .......

Percent of infants of low birth weight by period of gestation and race: Total of 42 reporting

States and the District of Columbia, 1976 ............... ........... ......... ........................... ....................

Pexent of infants of low birth weight by age of mother and race of child: United States, 1976 .....

Percent of infants of low birth weight among single live births and among Iivc births in plural

deliveries by period of gestation: Total of 42 rcponing States and the Dktrict of Columbia, 1976.

LIST OF TEXT TABLES

Number and percent distribution of infanu’ by birth weight and color: United States, 1950,

1966, and 1976 .................................................................................................. ............ ..............

1

1

3

3

5

5

5

:

10

12

12

14

15

15

16

19

21

23

3!)

36

37

3

4

7

9

12

6

...

Ill
B.

c.

D.

E.

F.

G.

H.

J.

K.

L.

M.

N.

o.

P.

Q.

R.

s.

T.

Percent distribution of infants of low birth weight by period of gestation according to race: Total

of 42 reporting States and the District of Columbia, 1976 .................................... .........................

Percent of infants of low birth weight for native-born and foreign-born mothers, by race of child:

United States, 1976 ....... ............. .................. ..................................................... .............................

Percent of infants of low birth weight by educational attainment and nativity of mother, and race

of child: Total of 44 reporting States and the District of Columbia, 1976 ................................... ..

Percent of infants of low birth weight by age of mother and race of child: United States, 1976 ....

Percent of infants of low birth weight by educational attainment of mother, age of mother, and

race of child: Total of 44 reporting States and the District of Columbia, 1976 ....................... .......

Percent of infants of low birth weight by age of mother, and live-birth order and race of child:

United States, 1976 .................. ...... ............. ...................................................................................

Percent of infants of low birth weight, by age of mother, pluraIity of birth, and race of child:

United States, 1976 ........................................... .............................................................................

Percent of infants of low birth weight by sex, plurafity of buth, and race: United States, 1976 ....

Percent of infants of low birth weight by marital status and age of mother, and race of child:

Total of 38 reporting States and the District of Columbia, 1976 . ...................................................

7

7

8

8

10

11

12

12

13

Percent of infants of low birth weight by marital status and edueationaf attainment of mother,

and race of child: Total of 35 reporting States and the Dktnct of Columbm, 1976 ................... .... “ 14

‘Percent of infants of low birth weight by maritaf status and area of residence of mother and race

of ehffd: Totaf of 38 reporting States snd the District of Columbia, 1976 . ....................................

Percent of infants of low bxth weight by educational at@nment of mother and race of child:

Totaf of 44 reporting States and the District of Columbia, 1976 . ................................................. ..

Observed and adjusted percent of infants of low birth weight by age of mother, month of pregnancy prenataf care began, and race of child: Totaf of 41 reporting States and the District of

Columbia, 1976 ................ .................................................................................... ..........................

Percent of infants of low birth weight by month of pregnancy prenatal care began, marital status

of mother, and race of chifd: Total of 34 reporting States and the District of Columbia, 1976 ......

Percent of single-live-birth infants of low birth weight by outcome of last pregnancy, interval

since termination of last pregnancy, and race of child: Total of 43 reporting States and the District of Columbia, 1976 ............... ....................................................... .......................................... ..

Percent of singfe-live-birth infants of low birth weight by age of mother, interwd since last live

birth, and race of child: Total of 43 reporting States and the District of Columbia, 1976 ..............

Percent distribution of single live births by interval since termination of last pregnancy, according

to race of child and birth weight: Total of 43 reporting States and the District of Columbia,

1976 . ..... .................................................... .................. ............ .......................................................

Percent of infants of low birth weight by educational attainment of mother, sise of place of residence, and race of child: Totaf of 44 reporting States and the District of Columbia, 1976 . ...........

14

15

16

17

17

18

19

20

.

.

iv
\

SYMBOLS

I

Data not availablc–—--—–– ..-

] Category not applicabk-——-–-—-- . . .

Quantity zero-–—–-———— .

Quanti~ more than Obut less than 0.05—- 0.0

Figure does not meet standards of

reliability or precision *

I
“

.

.

.

FACTORS ASSOCIATED WITH

LOW BIRTH WEIGHT

Selma Taffel, Division of Vital Statistics

INTRODUCTION

The physical maturity of a newborn infant

can be judged by its weight at birth or its gestatimud age (number of completed weeks of pregnancy measured from the first day of the last

normal menstrual period). Weight at birth has

been used more widely because it is accurately

and comp]ctcly reported; the accuracy of gestationid age, however, depends on the mother’s

correct recall of the date of the last menstrual

period.

Infmts weighing 2,500 grams (5 1/2 pounds)

or lCSSat birth are considered to be of low birth

weight. This criterion was recommended by the

American Academy of Pediatrics in 1935 and

adopted by the World Health Organization in

the Sixth Revision of the International Lists of

~iseascs and causes of Death (1948). Low-t) kthweight infants may be either premature, that is,

born before 37 weeks of gestation, or full term

but small for their gestational age.

The association between low birth weight

and a greatly elevated risk of infant mortality,l YZ

congenital malformations,~ mental. retardation,~

and other physical and neurological im airments5*6 Y. is well established. A recent survey mindicatesthat low-birth-weight infants are likely

to have low Apgar scoresa and to be delivered by

‘The Apgar score is an international code for the

clinical evaluation of an infant’s physiological condition

1 and 5 minutes after birth. A low score indicates some

doubt about the survival and subsequent health of the

infant.

cesarean section or in a breech position, with the

associated dangers to both mother and child.

Although only a relatively small proportion

of all newborns are of low birth weight, this,

group of births accounts for more than half

of aIl infant deaths (under 1 year), and nearly

three-quarters of all neonatal deaths (under 28

days), according to a national study of matched

birth and infant death certificates.1 In light of

the large number of deaths and the severe physic~ and mental hardcaps that often accompany

low birth weight, increasing attention has been

focused on some of the associated factors.

This report describes the patterns of occurrence of low birth weight in the United States

relative to demographic and health characteristics recorded on birth certificates. In addition,

recent trends in the incidence of low birth

weight are examined. The information presented

here is derived from entries on live birth certificates fded throughout the United States. However, when describing certain variables, for example, education or marital status of the mother,

the data are drawn from a more limited group of

reporting States, since not all State birth certificates include questions on some items. (See appendix I for a list of reporting areas for each

variable.)

SUMMARY OF PRINCIPAL FINDINGS

According to information derived from 1976

birth certificates, the incidence of low birth

weight in the United States varies widely by

race and by mother’s age, marital status, place of

residence, nativity, and pregnancy history. However, the socioeconomic status of the family as

1
measured by the mother’s educational attainment appears to be one of the most critical factors in determining birth weight. The proportion

of infants of low birth weight born to mothers

with 16 years or more of education (4.9 percent) was half that of infants born to mothers

with less than 9 years of education (9.9 percent).

From 1950 to the mid-1960’s there was a

gradual increase in the incidence of low birth

weight in the United States from 7.5 percent to

8.3 percent, followed by a general decline in incidence in the next decade. However, by 1976,

the incidence of low birth weight (7.3 percent)

was only slightly below the 1950 level. The rise

reflects the substantial increases in low birth

weight among white infants for nonhospital deliveries and among all otherb infants for both

hospital and nonhospital deliveries. For the

entire period 1950-76, the incidence of low

birth weight was consistently higher among all

other infants than among white infants, and this

difference increased progressively. By 1976, the

risk of low birth weight was twice as great for

infants of other races (12.1 percent) as for white

infants (6.1 percent).

Comparing racial and ethnic groups, it. was

found that the incidence of low birth weight in

1976 was highest among black infants (13.0 percent) and lowest among Chinese infants (5.7 percent). Although black babies were far more

likely than white babies to be of low birth

weight when born at full term, among premature

infants (less than 37 weeks’ gestation), the incidence of low birth weight was, on the average,

only slightly higher among black babies. Foreignborn mothers, regardless of race, were less apt to

bear a low-birth-weight baby than were nativeborn mothers. For almost all racial and ethnic

groups, higher levels of education were associated with a lower incidence of low birth weight.

Very young mothers and mothers in the

later years of childbearing were most likely and

mothers aged 25-29 years were least likely to

bear a low-birth-weight baby. The incidence of

low birth weight in 1976 ranged from 6.0 percent of infants born to 25-29-year-old mothers

to 10.5 percent of infants born to 45-49-year-old

mothers and 14.8 percent of infants born to girls

bA~ used throughout this report, the term “a”

other” refers to the combined grouping of all races other

than white.

under 15 years of age. The risk of low birth

weight for infants born to teenage mothers decreased with each successive year of the mother’s

age, declining to 8.8 percent of infants born to

19-year-old mothers.

For each age group, the incidence of low

birth weight varied with the birth order of the

child. The incidence was lowest for infants born

to women 25-29 years old bearing their second

child (5.1 percent), quite high for children born

to women 15-19 years old bearing a fourth or

higher order child (20.3 percent ), and highest

for babies born to girls under 15 years old bearing their second child (30.5 percent).

At all ages, unmarried mothers were more

likely than were married mothers to bear a lowbirth-weight baby. Overall, in 1976 the incidence of Iow birth weight was twice as high for

infants born out of wedlock (12.6 percent) than

for other infants (6,4 percent). Increasing educational attainment for both married and unmarried mothers was associated with a reduction in

the incidence of low birth weight, but this was

less pronounced for out-of-wedlock infants.

Regardless of age, mothers were least likely

to bear a low-birth-weight baby when the interval between births was 2-4 years. The incidence

of low birth weight was especially marked for

fourth and higher order births to teenage

mothers and mothers in their early twenties, an

indication of the detrimental effect of the close

spacing of births. The outcome of the previous

pregnancy was also found to be related to the

birth weight of the current birth–a previous

pregnancy terminating in fetal death increased

the likelihood that the current birth would be of

low birth weight.

Although the initiation of prenatal care early

in pregnancy was associated with a decline in the

incidence of low birth weight, a substantial part

of this decrease can be explained by the higher

educational attainment of the mothers who

started care early. Regardless of when prenatal

care was begun, there was a higher risk of low

birth weight among out-of-wedlock than among

other infants.

Live births in plural deliveries were about 9

times as likely to be of low birth weight than

were those in single deliveries (54.3 percent

compared with 6.3 percent). Part of this difference is due to the reduced gestational period of

infants in plural deliveries. Female babies were

2
more likely to be of low birth weight than were

male babies regardless of whether the birth was

single or part of a plural delivery.

Both white and black mothers living in large

urban places were more likely than were

mothers residing in small urban places to bear a

low-birth-weight baby. The lowest incidence of

low birth weight was among infants born to

mothers residing in primarily rural areas. The

proportion of low-birth-weight babies was highest in the South Region (8.0 percent) and lowest

in the West Region (6.4 percent), but some of

the regional differences were due to variations in

the proportions of black births.

.

RECENT TRENDS IN THE INCIDENCE

OF LOW BIRTH WEIGHT

- Collecting low-birth-weight data on a national scale became possible in 1949 when the

U.S. Standard Certificate of Live Birth was revised to include a question on birth weight;

these national data were first published in 1950.

From 1950 to the mid-1960’s the incidence of

low birth weight among all live births changed

only slightly, increasing gradually from 7.5 percent in 1950 to 8.3 percent in 1965 and 1966.

Since then, there has been a very gradual decline, but by 1976 the incidence of low birth

weight (7.3 percent) was only slightly below the

1950 level of 7.5 percent (table 1 and figure 1).

.

.

_ All rsces

. . .. ... white

15-

.— . Black

----- All racesother

14 -

thanwhm

/- ----

. .-. ::\,.\.\

!3 -

-/’ ‘\ /- -_. -” -. ..X

,“

~--.

12-

--

,,~

/

$ 11- /~” --

; ,’

w 10-

n.

‘t

““”- ..........

6 1 ! 1 , 8

1950 1955 1960 1905 1970 1975

YEAR

Figure 1. Percent of infants of low birth weight by race:

United States, 1950-76

Among white infants, there was little change

in the occurrence of low birth weight between

1950 and 1966, the proportion varying between

6.7 and 7.2 percent during this period. Since

1966, there has been a continuous decline in the

proportion of infants of low birth weight, from

7.2 percent in 1966 to 6.1 percent in 1976. For

all other infants the proportion low birth weight

rose aImost continuously from a low of 10.2

percent in 1950 to peaks of 13.9 percent in

1964 and 1966. This rise is a reflection of substantial increases in the incidence of low birth

weight among both hospit#- and nonhospitaldelivered infants during this period. Only a small

part of the increased incidence can be attributed

to increases in completeness of birth registration

and more accurate recording of birth weight

which were concomitmit with the rise in hospital

deliveries. If there had been no change from

1950 to the late 1960’s in the proportion of infants delivered in hospitals, the percent of infants of low birth weight would have risen from

10.2 percent in 1950 to 13.4 percent rather than

the observed 13.7 in 1968. This observation is

based on 1968 data adjusted by the direct

method of standardization, since the necessary

information is not available for the year 1966

(see appendix III).

Since 1966 there has been a gradual decline

in the incidence of low birth weight for infants

of all other races, but in 1976, the proportion

low birth weight (12.1 percent) was higher than

it had been in 1950 (10.2 percent). Weight at

birth was not tabulated separately for black infants prior to 1969. From 1969 to 1976 the percent low birth weight among black infants declined from 14.1 percent to 13.0 percent.

During the entire period 1950-76, the percent low birth weight was consistently higher

among aIl other than among white infants, and

the difference between these groups has increased progressively. In 1950, the risk of low

birth weight was 44 percent higher for all other

than for white infants (10.2 percent compared

with 7.1 percent); by 1976, the risk was twice as

great for all other infants (12.1 percent compared with 6.1 percent).

Age and Birth Order Changes

Two factors strongly associated with an infant’s weight at birth are the mother’s age at

3
time of birth and the birth order of the child.

(See “Age of Mother and Birth Order” in

“Demographic Correlates”.) These elements

have undergone considerable change since 1950.

. For example, the proportion of infants born to

teenagers increased from 12 percent to 18 percent of all births in the period 1950-76, concomitant with a drop in the proportion of infants

born to mothers aged 35 years and over from 11

percent to 4 percent of all births. At the same

time, first-order births increased from 32 percent to 42 percent of all births; fourth- and

“higher-order births halved in importance, from

21 percent to 11 percent of all births.

Teenage girls and older mothers are more

likely than are women of other age groups to

bear a low-birth-weight baby. Similarly, there is

an increased risk of low birth weight for first

births and fourth- and higher order births. However, as mentioned earlier, there have bien compensatory changes since 1950 in the proportion

of births in these high-risk groups. The question,

therefore, arises as to how much of the fluctuation ‘in the percent low birth weight since 1950

can be attributed to age and birth-order changes.

Information on birth weight by age of

mother was not available prior to 1955, and information on the age of mother cross-classified

by birth order was not available prior to 1965.

An analysis of changes since 1955 in the ages at

which white mothers were bearing children indicates “that“changes in age had only a minimal ef-

. feet on either the rise in the percent low birth

weight between 1955 and 1966 or on the subsequent drop following the 1966 peak. Changes

in the ages at which all other mothers were

bearing children tended to intensify slightly

the rise in the percent low birth weight

between 1955 and 1966 (by an additional 0.3

percentage points, or 2.5 percent). In other

words, the percent low birth weight would have

risen only 1.8 percentage points, rather than the

observed 2.1 percentage points, if the age

distribution of all other mothers had remained

constant. However, from 1966 to 1976 changes

in the age distribution of all other mothers had

no effect on the decline in the percent low birth

weight, (The direct method of standardization

was used for this analysis; see appendix 111.)

It was impossible to analyze the simultaneous effect of age of mother and birth-order

changes on the percent low birth weight for

years prior to 1965. Figure 2 depicts the actual

percent low birth weight for white and all other

babies for the years 1966-76 and the hypothetical percents that would have occurred if there

had been no change in the percent low birth

weight for each age-order group since 1965. The

solid and broken lines are the linear fits of these

points from 1966 to 1976. The slope of the

broken line represents the part of the decline in

the percent low birth weight which is attribut.

able to the change in the age-birth order distribution of births. The remainder of the decliie,

the difference between the broken line and the

solid line, can be ascribed to other factors. For

white ,infants, only 18 percent of the overall decline was due to changes in the age-birth-order .

distribution. of births; for all other infants, the

entire decline was due to other” causes.

.

0 Actualpwmnt low

birth wnl.jht

A Adj.md pmmt low

birth Wi@t

(A$9’kwl COntum *

cfdcr XWClllc P&t

low blnh Wloht

situ 1966)-

14.0 All other births ~

&+A-a— *-—&-& —

‘A

@

13.5-

13,0-

@

12,5- 0

1-

~

: 12.0-

2

f

I

7.5

t

Whitebirths

7.0 - -A- A_ & A -.

0

6,6 - a

w

6.0 I 1 8 t 1

1966 1968 1970 1972 1974 1976

YEAR

.

Figure 2. Actual and adjusted” percent of Infants of low birth

weight, by color: United Statas, 1966-76

4
Many factors other than age, birth order,

and place of delivery are known to reassociated

with low birth weight, and any changes over

time in the prevalence of such factors would

influence national trends in low birth weight.

Low socioeconomic status,s inadequate prenatal

nutrition,g~10 alcohol consumption,l 1 maternal

smoking, ‘ z and lack of prenatal care18 have aII

been identified as contributory causes. Additionally, changes in the incidence of elective inductionslq and in contraceptive utilization and the

frequency of abortionl 5 independent of their

effect on age and birth order have a bearing on

.

the overall incidence of low birth weight. It was

not possible, from information avatiable for this

report, to analyze how trends in the overall incidence of low birth weight have been affected by

such changes.

-,

Weight Distribution Changes

To obtain a clearer picture of the patterns of

low-birth-weight incidence, the percent &tribution of infants by birth weight (500-gram

intervals) for the years 1950, 1966, and 1976

are shown in table A.

During the period 1950-66 there was ahnost

no change in the overall percent of low birth

weight for white infants (from 7.1 percent in

1950 to 7.2 percent in 1966), and the weight

distribution remained virtually the same, except

for the moderate reduction of 18 percent in the

proportion of very large babies (weighing 4,501

grams or more). For all other infants, the overzdl

rise ih the percent low birth weight (from 10.2

percent to 13.9 percent) reflects a distinct shift

.

in the entire distribution toward lower weight.

In the period of declining incidence of low

birth weight (1966-76), the shift from lower

birth weight categories to higher ones was more

.

pronounced for white than for all other infants.

The greater reductions for white than for all

other births in nearly all the lower weight

categories are reflected in the sharper decline

(15.3 percent) in the incidence of low birth

weight for white infants than for all others (12.9

percent) during this period.

PERIOD OF GESTATION

It has become increasingly clear that there

are major differences in the health status of

low-birth-weight infants that are related to the

period of intrauterine growth. For example,

low-birth-weight infants with very short gestational periods have a neonatal mortality rate

about twice as high as that of other low-birthweight infants, but low-birth-weight babies with

the longest gestational periods are more likely to

be born with severe congenital anomalies.1 G It is

presumed that the Iow birth weight of babies

born at or near full term reflects intrauterine

maldevelopment and/or retarded growth.1 T

In 1976, 55 percent of all low-birth-weight

babies were born prematurely, that is, with

ge~tational periods of less than 37 weeks; 45

percent were full-term births (table B). There

was little difference between races in the incidence of prematurity among low-birth-weight

infants; 54 percent of white infants and 56

percent of black infants were born prematurely.

However, as shown in table B, there was a

greater likeIiiood that black infants would have

extremely short gestational periods.

Black babies were far more likely than white

babies to be of low birth weight when born at

full term (6.3 percent compared with 2.8 percent) but among premature babies, the incidence

of low birth weight was, on the average, only

dightly higher among black babies (42.9 percent

compared with 41.9 percent). Indeed, up to 36

weeks of gestation, the incidence of low birth

weight was lower for black than for white babies

(table 2 and figure 3). In 1976 the median

weight of black infants born before 36 weeks of

gestation was about 60 grams more than that of

white infants, but at longer gestational periods, *

blacks infants weighed an average of 200 grams

less than white infants. Thus it appears that the

fetal growth of black babies is generally slower

than that of white babies in late pregnancy

despite an initial advantage.’It has been hypothesized that social disadvantage may be the critical

factor explaining this racial difference in birth

weight at later gestational ages. Several studies

have shown a relationship between growth retardation in late pregnancy and adverse social or

environmentzd conditions.]s J9

DEMOGRAPHIC CORRELATES

Race and Mother’s Nativity

Two of the most important predictors of

birth weight are the race of the child and

5
Table A. Number and percent distribution of infants by birth weight and color: United States, 1950, 1966, and 1976

Birth weight

1 1

2,001- 2,501- 3,001 - 3,501- 114,001- 4,501

2,600 3,000 3,500 4,000 Not 4,500

grams grams grams grams grams CK%L ‘mtec’

2,500

grams

or less

Color and year Total

All races ,?, -

1976:: ................

1966 ..................

19501 ................

(9-! ’-(

1976..., ..............

1966 ..................

1950 ..................

Number

148,235 543,549

199,036 713,454

16B,571 607,855

Percant distribution

3,167,788

II

19,546 44,691

3,608,214 24,688 58.650

3,554,149 19,928 46,441 I

1,185,890 888,433 259,081 54,234

1,382,170 913,296 240,970 47,946

1,269,213 882,047 248,949

37.6 28.1 I

8.2 1.7 . . .

38.4 25.4 6.7 1.3 . . .

37.9 28.9 7.5 1,9 . . .

L,?

100.0 I‘7.3 0.6 0.6

100,0 8.3 0.6 0.7

100.0 7.5 0.4 0.6

1.4 4.7 17.2

1.6 5.5 19.8

1.4 5.1 18.3

Percent change

-12.5 -14.5 -13.1

14.3 7.8 8.2

.

-2.3 10.6 22.4 I

30.8 . . .

1.3 -5.6 -10.7 -31.6 . . .

. . .

II -12.0 -16.7 -14.3

. . . 10.7 60.0 11.7

1866-~8 .............

19506,6 .............

White

1976

1886;:.:::::::::

19501 ...............!

!, ‘1

1976 .................

1966 .................

1950., ...............

Number

103,224 I

397,951

145,222 551,158

137,195 509,521

“

49,361

42,504

48,606

1.9

1,4

1.7

7,427

5,824

201,912

.,.

. . .

. . .

954,073

1,154.788

1,086,735

768,354

805,504

787,607

233,471

2t7,726

217,336

9.1

7.3

7.6

2,567,614

II

156,977 10,493

2,993,230 215,720 13,326

3,063,627 202,010 11,482

/ ,.

3,

12,636

16,870

15,855

30,424

40,302

37,478

Peraent distribution

0.4 0.5 1.2 4.0 15.6

0.4 0.6 1.3 4.9 18.4

0.4 0.6 1.3 4.8 17.8

37.3 I

30.0

38.7 27.0

38.3 27.6

100.0 I

6.1

100.0

100.0 ;:

Percent change

-3,6 11.1 24,7

I

35.7 . . .

1.0 -1.8 -3.9 -17.6 . . .

. . .

II -15.3 - -16,7 -7.7 -16.4 -15.8

. . . 1.4 --- 2.1 3.4

1886-76 .............

1960-66 .............

All other

1976.,., ..............

1886 ..................

19501 ................

,.<. .

1976 .................

1956 .................

1950 .............<...

Number

14,267 45,011

16,348

8,863 31,376

Percent diatributionz

2.4

I

24.3

2.7 :: 26.6

2.0 6.8 21.4

Percent change

231,817

227,364

162,476

38.7

37.2

35.4

1,819

2,260

31.437

118,079 I

25,590

107,792 23,244

104,s40 31,613

4,873

5,442

15,076

600,174 72,398

613,044 84,634

490,522 47,044

?!,‘,.

100.0

II

12.1

100.0 13.9

100.0 10.2

6,410 I

6,710

6,654 7,618

2,632 4,073

19.7 I

4.3

17.6 3.8

22.8 6.9

0.8

0.9

3.3

1.1 1.1

1.1

0.6 F9

. . .

. . .

. . .

. . . -12.9 - -15.4 -11.1 -14.6 -6.6 4.0 11.9 13.2 -11.1 . . .

. . . 36.3 83.3 44.4 35.0 28.4 24.3 5.1 -22.8 -44,9 -72.7 . . .

1966-76, ...........

195S66 ............

1In 1950 birth Waight Wa$ not ~ecorded for b~hs in Connecticut and Massachusetts. Births io these S~tes are included in the’’not stated’’claasification.

2To~aI ~x~l~d~$ not stated birth weight.

whether the mother is native- or foreign-born. among white babies. The lowest incidence was

As shown in table C, there are very large for Chinese-American babies (5.7 percent); the

variations among the major racial groups in the levels for American Indian babies (6.9 percent)

incidence of low birth weight. Black babies are and Japanese-American babies (7.2 Percent)

more than twice as likely as white babies are to were higher than those for white babies, but

be of low birth weight. In 1976 the percent of substantially less than those for black babies.

infants of low birth weight was 13.0 percent In general, foreign-born mothers, regardless

among black babies compared with 6.1 percent of race, were less apt to bear a low-birth-weight
.

.

Table B. Percent distribution of infants of low birth weight by

period of gestation according to race: Total of 42 reporting

States and the District of Columbia, 1976

,

I II I

Period of gestation All IIWhite Black racesl

Total..., ......................... 100.0 100.0 100,0

Under 37 weeks .............................. 54,6 64.0 66.3

37-weeks and over ,,,,,...,.,,.,,..., ....... 45.4 46.0 43.7

Under 28 weeks .............................. 7,2 6.5 9.1

28-31 weeks,.,,!............................... 10.6 10.1 11.9

32-3S weeks.................................... 27.5 28.0 26.3

3S weeks..,,.., .................................. 9.3 9.4 8.9

37.39 weeks.................................... 29.0 29.3 26.0

40 weeks..., ..................................... 7.0 6.4

4142 weeks.................................... 6,2 :::

43 weeks and ovar .......................... 3.2 3.1 2!

lIncludes races other than white and bleck.

2Excludes birth.q for which period of ge6tRt~Ofl WS 230t

stated.

90r

80 ~,

\

\

i.

70 -

~.

‘. \

‘\

eu -

‘\,

‘\

\

+ 50 - ekc;~,

~

\

\

~40 -

\

\

\

. \

\

30 -

20 -

10 -

------ --

2:2728 2S 33 31 32 33 34 36 20 37 2S 39 40 41 4243md

m

GESTATION IN WEEKS

Figure 3. Percent of infants of low birth weight by period of

gestation and race: Total of 42 reporting States and the

District of Columbie, 1976

baby than were native-born mothers (table C).

The most pronounced difference was for black

and Chinese births, where the incidence of low

birth weight was about 50 percent higher for

native-born than for foreign-born mothers.

Table C. Percent of infants of low birth weight for nativa-born

and foraign-born mothars, by race of child: United Statas, 1976

Rata of child

Native1ForeignTotal 1 born born

mother2 mother

All races

““’”””””””””””” w~

White .....................................

81eok.....................................

American Indian ....................

Chinese..................................

Japanese................................

Other rssces.,.,..,.,,..................

6.1

13.0

6.9

S,7

7.2

7.1

6.2

13.2

6,9

7.7

8.0

7.6

5,8

8,8

8.3

5,2

6.2

6,9

lhtcludes unkno~ nativity.

2Born ~ the United HateS.

Among foreign-born white mothers, women

born in Puerto Rico were far more likely than

were women born in Cuba or Mexico to give

birth to a low-birth-weight baby. The incidence

of low-birth weight for infants born to Puerto

Rican-born mothers. was 9.0 percent compared

with the very low incidence of 5.2 percent for

infants born to mothers born in Cuba and 5.4

percent for mothers born in Mexico (table D).

For almost aIl racial groups, higher leveIs of

educational attainment of the mother were

associated with a pronounced decrease in the

proportion of low-birth-weight babies (table D).

This was especially noticeable for white infants,

where the incidence of low birth weight in 1976

was about 42 percent lower for births to women

with 13 or more years of schooling than for

births to women who had not completed high

schooL For black infants, the comparable difference in the incidence of Iow birth weight was 28

percent. The much lower incidence of low birth

weight among black babies born to better

educated mothers suggests that the generally

lower birth weight of black babies is influenced

to a great extent by environmental factors. (For

a further discussion see “Period of Gestation.”)

The variation in the incidence of low birth

weight among infants born to mothers of different racial groups was slightly less for infants

born to mothers with 12 years or more of

education than it was for infants born to

mothers with less than 12 years of education, an

additional indication that racial clifferences in

birth weight can be explained in part by

socioeconomic factors.

7
Table D. Percent of infants of low birth weight by educational attainment and nativity of mother, and race of child: Total of 44

reporting States and the District of Columbia, 1976

Race of child and mother’s nativity

All races ..................... ............................ .......... ...... ......................................... .....

White ....... .................................................................. ..................................... .........

Native-born 1....................... .. .......... .... ...... .............. .............................................................

Foraign-born:

Puerto Rican ................................... ............ ........... .........................................................

Cuban ........ .................. .......................................... ......................... ................................

Mexican ................. ............ ........... ......................... .... ...... .. .... .. ................... ....................

Other foreign-born ............ ....... ...... ....................... ............. ...... .......................................

Not stated ...................................... ...... .......... ............ ...... .... .................... ........ ....................

Black ................................ ........................ .. ............... ................................................

Native.born 1..................... ................................. ................. ....... ...... ...... ..............................

Foreign. born ......... ............ ..... ..... .................. ............ ..................................... ............ ..........

Not stated ................................................................................................................... .......+-

American Indian ......................... ...................... .................. ...................... ....... .........

Chinese ..................... .......... .. .......... ...... .. ...... ............................ ...... ..........................

Japanese ........ ..................... ....... ................. ........................ .......................................

Other races ......................... .................. ......................... ....................... .......... ...........

lBorn in the united s~t~s,

Age of Mother and

,Birth Order

Both mother’s age and the birth order of the

child are independently related to birth weight,

but the interaction of these two factors may

strengthen or moderate their individual effects.

The age of the mother and the birth order of the

child are in turn strongly related to socioeconomic factors that have a bearing on weight at

birth. The interrelationship of these factors as

they affect the incidence of low birth weight is

discussed in this section and in “Educational

Attainment of Mothers” in “Social Factors. ”

Agc of mother. —Very young mothers and

mothers in the oldest years of childbearing were

most apt to bear a low-birth-weight baby;

mothers in their twenties and early thirties were

least Iikcly to (table E). The pattern of a much

Years of school completed

12 years

6.8

5.8

5.8

8.6

4.5

5.8

5.6

6.5

12.0

12.2

9.2

10.9

6.6

6.2

7.8

7.0

3 years

)r mora

5.5

by mother

Total

Less than

12 years

7A 10.1

6.2 8.4

6.2 8.6

9.0 9.3

5.2 6.7

5.4 5.4

5.5 5.7

12.2 9.8

13.1 14.8

13.3 15.0

9.1 8.4

19.5 14.2

6.8 7.3

5.9 5.0

7.5 7.3

7,2 8.5

,

4.9

4.8

7.3

4.5

5.2

5.3

6.1

10.7

.

10.8

9.3

4.8

5.9

6.1

7.1

6.5

Table E. Percent of infants of low birth weightby e!leof

mother and race of child: United States, -l 976

Age of mother

All ages ......... ..................

Under 15 years ...............................

15-19 years ........................ .............

15 years .... .................................

16 years ....................... ......... .....

17 years .....................................

18 years ... .................... ..............

19 years .....................................

20-24 years ................ .. ............ .......

25-29 years .. ...................................

30-34 years ............... ......................

35-39 years ....... ........ ......................

40-44 years .............. .......................

45-49 years .....................................

1

All

1 White

races

1

7.3 6.1

14.8 11.8

9.9 8.1

12.4 10.0

11.5 9.4

10.4 8.5

9.8 8.0

8.8 7.2

7.1 6.0

6.0 5.3

6.5 5.8

.7.9 7.0

9.2 8.3

10.5 9.4

lInclud~~ races oth~~ than white and black.

Black

13.0

17.1

14.7 .

15.6

15.3

14.8

14.8

13.9

12.6

11.3

11.6

13.1

12.8

16.3

8
higher incidence of low birth weight for infants

born to very young mothers and older women is

evident for both white and black infants. However, at all ages, black mothers are far more

likely than are white mothers to bear a lowbirth-weight baby (figure 4).

For both racial groups, the proportion of

low-birth-weight babies generally increased progressively from the low observed for 25-29-yearold mothers as the age of mother increased or

decreased. For white infants, the percent low

birth weight varied from a low of 5.3 percent of

those born to mothers 25-29 years to 11.8

+ percent of infants born to girls under 15 years of

age and 9.4 percent of those born to women

45-49 years old. For black infants, the incidence

of low birth weight ranged from 11.3 percent of

. those born to 2B-29-year-old mothers to 17.1

percent of those born to girls under age 15 and

16.3 percent of infants born to 45-49-year-old

mothers.

There has been inc~easing concern in recent

years about the large number of births to

teenage girls. Such births are more likely to be

premature and of Iow birth weight than are

births to mothers in their twenties. Not only are

the infants of teenage mothers at greater risk,

.

Figure 4. Percent of infants of low birth weight by age of

mother and race of child: United States, 1976

18r\

\

\

16 -\

\

/

\

/

.\ /

\

\

14 -

\

//

\.

\

\

//

/-- _-/

\\ Shck / Z

12 -

\

\

$

/’

‘\ ----

;

&

10 -

s6-

1

Un&r 15

! , 1

15.19 2024 25.29 20.34 35.33 40.44 45.49

AGE OF MOTHER IN YEARS

but teenage mothers themselves are more likely

to suffer from complications of pregnancy than

are women in the optimum ages of childbearing.z 0 A major biological problem of pregnancy

for young teenagers is that the nutritional

requirements of the growing infant are superimposed on their own elevated needs during the

adolescent growth spurt. Yet, according tO a

recent survey, over half of all girls aged 15-17

years had less than the recommended intake of

protein, vitamin A, and vitamin C, and over 90

percent had less than the recommended intake

of iron.z 1

As shown in table E, girls under 15 years of

age had the highest risk of any age group of

bearing a low-birth-weight baby; the overaII

incidence for girls 15-19 years exceeded that for

all older age groups except women 45-49 years

old. The risk of Iow birth weight for infants

born to teenage mothers diminished with each

successive year of age—from 14.8 percent for

infants born to girls under 15 years of age to 8.8

percent for those born to 19-year-olds.

For mothers old enough to have completed

at least 12 years of education, increasing educational attainment was generally associated with a

reduced risk of bearing a low-birth-weight baby

(table F). Thus, for women aged 25-29 years,

the most favored age group, the proportion of

infants of low birth weight declined from a high

of 9.2 percent of those born to mothers with

9-11 years of education to a low of 4.8 percent

of infants born to women who had completed

16 years or more of education. For all age

groups, the incidence of low birth weight increased slightly for infants born to mothers with

9-11 years of education compared to those born

to mother with O-8 years of education. A

possible explanation for the lower risk of low

birth weight among children born to women

with minimal education is the fact that the

incidence of fetal deaths is highest among

women with the lowest educational attainment.

Thus a greater proportion of pregnancies of

women with low educational attainment may be

terminating in fetal death rather than in a

low-birth-weight live birth.

Age and birth order. –The pattern of a

higher risk of low birth weight for infants born

to very young girk and older women is seen for

9
Table F. Percent of infants of low birth weight by educational attainment of mother, age of mother, and race of child: Total of 44

reporting States and the District of Columbia, 1976

Age of mother and race

All racesl

20-24 years ............... ...... ........................ ........ .......... ............. ............. ..

25-29 years ........................... ......................... ...... ................. .. ..............

30-34 years ..... .......... .... ...... .................... ............ .................. .. ........... ...

35-39 years ... ................ ........ ...... .......................... .... ............................

40-49 years ........... ........ .................... ........ ................ ...... ......................

White

20-24 years ............ ..... ....... .................. ........ ........................ ........ .... .. ...

25-?9 years .... ....... ................. ........................................ ...... .................

30-34 years ..... .... .............. ..... .............. ......... ........................ ............ ....

35-39 years .. ............................................... ................ ........ ..................

40-49 years ... ..... ........ ........................... ......................... .............. .... .....

Black

20-24 yeers ........ ........ ...... ...... ............. ...... ........... ............. ........ ............

25-29 years ................................ ..................... .......................... ............

30-34 years ..................... ............................... .. ...... ............ .................. .

35-39 years ........ .................. ............. ................................ .. ...... ...... ......

40-49 vears ....... ...... ...... ........................................ ...... .............. ............

1Includes races other than white and black.

all birth orders (table G), an indication of the

critical influence of mother’s age. At each age,

however, there are substantial differences in the

incidence of low birth weight related to the

birth order of the child (table G).For infants

born to teenage mothers and mothers in thei~

early twenties, the incidence rose sharply for

fourth and higher order births. This probably

reflects the close spacing of such births, a factor

strongly related to an elevated risk of low birth

weight. (See “Outcome of Last Pregnancy and

Birth Interval”.) In contrast, the proportion of

low-birth-weight infants generally decreased for

higher order births to women 35 years of age

and over. The lowest incidence for any group

was for women aged 25-29 years bearing their

second child (5.1 percent); the highest was for

teenagers 15-19 years of age having a fourth or

higher order birth (20.3 percent ) and girls under

15 years of age having a second child (30.5

percent). In general, the lowest risk of low birth

weight occurred when the age of the mother and

the birth order of the child were compatible—for

example, when young mothers had first or

Total

7.3

6.1

6.6

8.2

9.5

6.1

5.3

5.8

7.1

8.6

12.8

11.5

11.7

13.3

13.0

9-11

years

9.6

9.2

9.8

11.3

12.1

7.9

7.8

8.6

10.0

11.6

14.4

13.5

13.2

14.4

12.9

Years of school completed by mother

O-8

years

9.1

8.1

8.8

9.5

10.5

8.1

7.1

7.7

8.4

9.8

14.2

13.3

13.4

13.1

13.4

12

years

6.7

6.1

6.8

7.8

8.8

5.7

5.4

6.1

6.9

8.0

12.1

11.0

11.2

12.8

12.8

13-15

years

6.3

5.3

5.8

7.2

7.8

5.3

4.8

5.2

6.5

7.1

11.4

10.5

10.6

12.5

10.7

16 years

or more

5.5

4.8

4.8

5.8

7.3

4.8

4.5

4.4

5.2

6.7

10.2

8.8

9.5

11.5

10.4

Not

stated

9.4

8,0

7.9

10.0

12.0

.

7.4

6.4

6.6

8.1 .

9.7

15.4

15.9

14.7

17,5

19.6

second births and older women had higher order

births.

Plurality of Birth

There are increased health risks for both the

mother and the infant when the birth is part of a.

plural delivery. According to a recent survey:, -

twice as many infants in plural as in single

deliveries had a l-minute Apgar score of 7 or

lessz z (an indication of moderate or severe

depression of the infant), 10 times as many were “

delivered in a breech position,23 and 4 times as

many mothers suffered one or more complications of Iabor.z 0 Other studies indicate that

perinatal and neonatal mortality is greatly elevated in twin pregnancies, that morbidity among

surviving twins is high, and that these outcomes

are more likely for the low-birth-weight

twin.z4 DZ5 Information from the present study

indicates that live births in plural deliveries are

about 9 times as likely to be of low birth weight

as single live births. The overall incidence of low

birth weight in 1976 was 54.3 percent for
Table G, Percent of infants of low birth weight by age of mother, and live-birth order and race of child: United States, 1976

Aae of mother

30-34

years

3539 40-44

years years

7,9 9.2

10.3 11.7

7.9 9.4

7.3 9.3

7.7 8.8

10.2 13.8

7.0 8.3

9.1 10.6

7.2 9,1

6.4 8.8

6.7 7.9

7.9 12.4

13.1 12.8

20.8 17.4

13.3 12.6

13.1 13.2

12.1 12.5

18.5 20.5

Live-birth order and race Total

Under

15 years

45-49

years

All racesl ......................... ................ ...... 7.3 14.8 -a-Y-l=

14.3

30.5

“1 5.4

16.4

11.8

6.5

7.9

5.7

5.6

::

5.8

7.2

5.2

5.1

6.2

7.3

11.6

10.5

15.2

9.3

12.4

10.2

9.4

First child ....... ....... ...............!.. ... .................. .. .......

Second child .......... ....... ................. ........................

Third child .................................................... .. .......

Fourth child and over .................... ............ .... .. .... ..

Not stated ........ ......... ...................... ...... .......... ...... .

7.6

6.5

:;

9.1

9.1 6.7

12.0 6.6

15.5 8.9

20.3 11.9

11.4 8.3

6.4

5.1

5.9

7.9

7.3

t

8.1 6.0

7.6 5.9

9.6 5.6

12.6 7.5

17.3 9.5

8.7 6.3

5.3

.

5.9

4.5

5.2

6.6

6.6

White ............................... ...... ..... ..... ....... .... 6.1

.

.

First child .. ...... ...... ............ ................... ..... ............

Second child ..... ..... ......................... ..... ..... ....... .... ..

Third child .. ...... ...... ........................ ....... ..... .......... .

Fourth child and over ................. ...... ...... .............. .

Not stated ......................... .... ...... .. ......... ............ ....

6.5

5.5

5.9

6.9

7.1

11.4

22.7

●33.3

17.3

17.1

13.0

7.1

13.8

9.0

Black ..... ..... ....... ........ .... ..... ...................... ... 16.3

l--

13.0

First chiid ....... ........... ................. ..................... ......

Second child ........................... .............. ....... ...... ....

Third child ....... .......... ........ .... ................ .... ............

Fourth child and ovar .. ........... ....... ............... .... .. ...

Not @ated .............. .................. ........... ...... .............

13.2

12.8

12.6

13.0

14.6

16.7

34.9

“10.0

15.0

13:7 12.0 12.2

17.0 12.1 10.2

15.0

10.6

10.3

11.7

15.0

‘40.0

21.7

●5.9

15.7

18.7 13.2 11.0

22.5 15.5 12.3

15.1 14.9 11.4

infants in pluraI deliveries compared with 6.3 teenager. The pattern of risk by age of mother

percent for infants in single deliveries (table H).

Perz”od of gestation. –The higher incidence of

low birth weight among infants in plural births is

accounted for in part by their reduced gestational period.z G In 1976 the median gestational

period of infants born in plural deliveries (37.8

weeks) was 21A weeks shorter than that of

infants in single deliveries (40.3 weeks). However, at all periods of gestation there was a far

greater risk of low birth weight for babies in

plural deliveries, and at full term, infants in

plural deliveries were , on the average, 11 times

more likely to be of low birth weight than

infants in single deliveries (table 3 and figure 5).

The intrauterine volume of twins at 32~z weeks

of gestation is close to that of a single infant at

full term.zs It has been suggested that the

constricted intrauterine environment and diminished uterine bloodflow in women pregnant with

more than one child limits full development and

growth.z 4

Age of mother. –For infants in both single

and multiple deliveries, there is a much higher

risk of low birth weight when the mother is a

for fifants in- single deliveries parallels that

described for all infants in a previous section–

that is, the incidence of low birth weight is

lowest for infants born to mothers 25-29 years

of age, with the incidence increasing as the age

of the mother increases or decreases. For infants

in phual deliveries, the percent of those of low

birth weight generally declined as the age of the

mother increased (tab~ H).

Sex. –Female babies were more likely than

male babies to be of low birth weight, regardless

of whether the birth was single or part of a

plural deIivery (table J). In 1976 there was a 20

percent greater incidence of Iow birth weight

among female inf~ts (7.9 percent) than male

infants (6.6 percent). About half (50.7 percent)

of alI male infants in twin deliveries were of low

birth weight compared with 56.6 percent of aIl

female infants in twin deliveries. The proportion

of infants of low birth weight was extremely

high for both male and females babies in triplet

and other plural deliveries (85.7 percent and

92.2 percent for male and female births, respectively).

.

<

11
Table Ii. Percent of infants of low birth weight, by age of mother, plurality of birth, and race of child: United States, 1976

Age of mother

Plurality and race Total

Under 1519 20-24 25-29 30-34 3539 40-44 4549

15 years years years years years years years years

All racesl ...... .. .... ................................... 7.3 14.8 9.9 7.1 6.0 6.5 7.9 9,2 10.5

Single live births ...... ............ ...................... ............ 6.3 14.1 9.2 6.2 5.0 5.5 6.8 8.3 10.1

Live births in plural deliveries ......... ...... ...... .......... . 54.3 71.7 67.1 57.8 50.4 47.7 49.0 46.7 “66.7

White .... .................... ............ ........ .......... .... 6.1 11.8 8.1 6.0 5.3 5.8 7.0 8.3 9.4

Single live births .. ................. ...... ............ .. ............. 5.3 11.1 7.4 5.2 4.4 4.8 5.9 7.5 9.0

Live births in plural deliveries ............ .... .. .............. 51.8 73.1 63.4 55.3 49.0 46.0 46.7 45.4 ●66.7

Biack .......... ........... ................... .... ... .... .. .... .. 13.0 17.1 14.7 12.6 11.3 11.6 13.1 12.8 16.3

.

Single live births ... ............... ... .... .. ........... ...... ........ 11.8 16.4 13.8 11.3 10.0 10.1 11.5 11.9 16.3

Live births in plural deliveries ................. ............... 64.1 69.5 74.0 66.8 58.6 54.8 57.2 50.0

Ilncludes races ~the~ than white and bl~ck.

____ \

\

..

90 -

\

\

\

\

\

80 \

\

\

70 -

60 -

50 -

l.im birlh, in plural

40 -

/

30 -

/

/

Single live births \ \ - - _ - ~

20 -

10 -

0 , , I

20-27 2S.31 32.35 36 3739 40 41.42 43 and

OWsr

GESTATION IN WEEKS

Figure 5. Percent of infants of low birth waight among singla

live births and among live births in plural deliveries by

period of gestation: Total of 42 reporting States and the

District of Columbia, 1976

.

Table J. Percent of infants of low birth weight by sex, plurality

of birth, and race: United States, 1976

Plurality of birth and race

All racesl .............. ..........

Single live births ..............................

Live births in twin deliveries ........ ...

Live births in other plural

deliveries ..... ... ..... .........................

White .... ........................... .....

Single live births ................... ...........

Live births in twin deliveries ....... ....

Live births in other plural

deliveries ............. .........................

Black ....................................

Singla live births ............ .. ................

Live births in twin deliveries ...........

Live births in othar plural

deliveries ............................ ...... .. ..

Total

7.3

6.2

53.7

89.1

6.1

5.3

51.1

88.6

13.0

11.8

63.7

89.1

Mala

6.6

5.8

50.7

85.7

5.6

4.8

48.3

85.9

11.7

10.6

60.3

83.5

Female

7.9

6.9

56.6

92.2

6.6

5.7

53.9

91.3

.

14.2

12.9

67.1

●

94.1

llncludes races other than white and black,

SOCIAL FACTORS

Marital Status

There have been substantial increases in the

number of infants born out of wedlock in recent

years, concomitant with a gradual decline in

12
.

.

.

.

general fertility. This has resulted in a dramatic

rise in the proportion of all births that are out of

wedlock.z 7 By 1976, 8 percent of all white

babies and 50 percent of all black babies were

-born out of wedIock. Previous studies have

documented the relatively greater health handicaps experienced by babies born out of wedlock.z ~zs In this study, a higher risk of low birth

weight was observed for out-of-wedlock infants,

even when demographic and socioeconomic differences were taken into account.

Age of mot/zer.-At all ages, unmarried

mothers were more likely than married mothers

to bear a low-birth-weight infant (table K). The

overall proportion of out-of-wedlock babies of

low birth weight (12.6 percent) was ahnost

twice as high as that for other babies (6.4

percent), but this differential was reduced considerably when mothers were in their teens or

aged 40 years and over.

Race. –For both black and white babies, the

risk of low birth weight increased substantially

for those born out of wedlock. For white infants

born out-of-wedlock, the incidence of Iow birth

weight in 1976 was 66 percent higher than for

other infants (9.8 percent compared with 5.9

percent ); for black babies it was 32 percent

higher (14.8 percent compared with 11.2 percent). Racial differences in the incidence of low

birth weight were less pronounced among outof-wedlock than among other infants. The proportion of infants of low birth weight was 51

percent higher among black than white out-ofwedlock infants (14.8 percent and 9.8 percent,

respectively), but among infants born to married

women, the proportion of those of low birth

weight was 90 percent higher among black

babies (11.2 percent and 5.9 percent, respectively).

Educational attainment.–For both out-ofwedlock and other infants, increasing educational attainment of the mother is associated

with a substantial decline in the incidence of low

birth weight. However, the decline is less pronounced among infants born out of wedlock

(tabIe L). The percent low birth weight declined

from 13.6 percent to 9.9 percent as the educational attainment of unmarried mothers increased from O-8 years to 16 years or more. The

comparable decline in low birth weight among

infants born to married mothers was from 8.7

percent to 4.8 percent. At higher levels of

educational attainment there were still substantial differences in the incidence of low birth

Table K. Percent of infants of low birth weight by marital status and age of mother, and race of child: Total of 38 reporting States and

tha District of Columbia, 1976

Age of mother

Total ...................................................................................................

Undar 15 years ....................................................................................................

15-19 years..........................................................................................................

15 years..........................................................................................................

16 years..........................................................................................................

18 years..........................................................................................................

19 years..........................................................................................................

20-24 years..........................................................................................................

2%29 years..........................................................................................................

30-34 years..........................................................................................................

35-39 years..........................................................................................................

40-44 years..........................................................................................................

4549 years............... ..........................................................................................

lIn~lude~ ~ace~other than white and black.

Married mothers

T

AH White

r-sl

6.4 5.9

i

12.9 12.6

8.2 7.6

10.6 10.4

9.6 9.1

8.3

:: 7.7

7.4 6.7

6.4 5.6

5.6 5.2

6.1 5.6

7.4 6.8

8.6 6.1

10.8 10.1

Black

11.2

20.0

13.7

16.8

15.4

14.6

13.8

12.8

11.1

10.3

10.6

11.7

12.1

15.4

Unmarried mothers

11

All

1 Whita

races

T

12.6 , 9.8

15.2 11.5

12.7 9.7

13.4 9.6

13.0 10.1

12.5 9.5

12.5 9.5

12.3 9.7

12.4 9.6

12.0 9.5

13.3 11.2

14.1 11.5

13.4 11.9

12.5 12.5

Black

14.8

17.0

15.0

15.9

15.3

14.8

15.0

14.4

14.5

13.8

15.0

16.4

14.5

12.8

13
Table L. Percent of infents of low birth weight by marital stetus and educational attainment of mother, and rata of child: Total of 36

reporting States and tha District of Columbia, 1976

Married mothers Unmarried mothers

Years of school completed by mother

All White Black All

races1 1 White

reces

Black

Total 2 ................................................................................................. 6.4 5.8 11.1 12.7 9,8 14.8

08 yaars........................................................................................ ..................... 8,7 8,2 13.0 13.6

911 years

10,8 16,4

...,.,,,.,,,...,,.. ......................................................................................... 8.6 7.9 12.7 13.2

12 years............................................................................................................... 6.1 5.6

10.3 16.4

10.7 11,7 9.0

13-15 years

13.6

.......................................................................................................... &4 S,o 10.0 11.7 9.2

16 years or more ................................................................................................. 4.8 4.4 Q.o g,g 7.5

13.3

12.0

llncludea races other than white and black.

21ncludes years of school not stated.

weight between out-of wedlock and other infants. Indeed, this differential generally increased with additional years of education for

both major racial groups.

Area of residence.–As shown in table M,

there are major differences in the incidence of

low birth weight by marital status in both

metropolitan and nonmetropolitan areas. In

metropolitan areas, the proportion of low-birthweight babies was more than twice as high for

unmarried as for married mothers (13.0 percent

compared with 6.4 percent); in non-metropolitan areas, this differential was reduced slightly

to 87 percent (11.8 percent compared with 6.3

Table M. Percant of infants of low birth weight by marital

status and area of residence of mothar end race of child:

Total of 38 reporting Statas and the District of Columbia,

1976

I I

Residance of mother and Married Unmarried

race of child mothers mothers

All racasl ................................

Metropolitan areas .............................

Nonmatropolitan areas.......................

w

White ............................................

Metropolitan arees .............................

Nonmetropolitan areas.......................

w

Black ............................................

Metropolitan areas .............................

Nonmetropolitan areas....................... H-1-%

lInc]udes races other than white and black.

14

.

percent). The percent low birth weight among

infants born out of wedlock was 10 percent

higher for mothers residing in metropolitan areas

compared with nonmetropolitan areas; among

infants born to married mothers, the incidence

of low birth weight was approximately the same

in both areas.

Some of the differential in the incidence of

low birth weight by marital status can be

explained by differences in the age and educational attainment of the mother. If these factors

are held constant, the differential in incidence is

reduced by 9 percent among white infants and

by 38 percent among black infants. It is apparent that there are additional determinants that

maintain the wide differential by marital status

within each racial group. It has been noted that

the unmarried mother faces greater economic

and emotional difficulties which may adversely

affect the early development of her baby.2 g

These factors may also be involved in the

persistent elevation in the incidence of low birth

weight among infants born out of wedlock.

Educational Attainment of Mother

Questions on the educational attainment of

parents were added to the 1968 revision of the

Standard Certificate of Live Birth to provide a

measure of the socioeconomic status of the

family. Since the educational attainment of the

mother and father are highly correlated and the

father’s education is generally missing from birth

certificates of infants born out of wedlock, the

mother’s education was chosen for analysis in

this report.
.

4

.

Table N shows that the proportion of

low-birth-weight babies born to mothers with 16

years or more of education (4.9 percent) was

half that of babies born to mothers with less

than 9 years of education (9.9 percent). An

inverse relationship between the incidence of

low birth weight and educational attainment was

found for each racial group, independent of age,

nativity, marital status and residence of mother,

and timing of prenatal care. (This is discussed in

more detail in “Race and Mother’s Nativity,”

“Age of Mother and Birth Order,” “Marital

Status, “ “Prenatal Care,” and “Geographic Variations.”)

Table N. Percent of infants of low birth weight by educational

attainment of mother and race of child: Total of 44

reporting States and the District of Columbia, 1976

I II I

Years of school completad I

All

by mothar IIWhite Black

racesl

Total ......... ... .. .......... ............ 7.4 6.2

0-8 years ........... ........ ...... ................ 9.9 . 8.6

911 years .... ...... ...................... ...... . 10.2 8.4

12 years ......................... ................. 6.8 5.8

13-15 years .. .......... ................... ...... 5.9 5.1

16 years or more ............................. 4.9 4.5

Not stated....................................... 9.5 7.4

13.1

14.9

14.7

12.0

11.2

9.4

16.0

It has been noted that a number of factors

associated with low socioeconomic status may

be related to a less favorable outcome of

p~e~mcy.2 g These include ~inimal education,

low income, inadequate nutrition, maternal

work and fatigue, and a history of deprivation in

the mother’s own childhood. The decreased risk

of low birth weight associated with higher levels

of education may thus be due to increased

nutritional knowledge and the resources to

apply this knowledge, a greater interest in health

care, and a higher level of prepregnancy health.

PREGNANCY HISTORY

Prenatal Care

The early initiation of prenatal care is generally regarded as crucial for the identification and

correction of any existing medical and obstetrical problems. It is difficult to ascertain whether

prenatal care has an effect on birth weight since

mothers who seek early and continuous care are

also likely to be in the most favored socioeconomic groups. The prevalence of low birth weight

has been related to the source of prenatal care

(private versus public services),l g the poverty

status of the area of residences 0 and as discussed in the section “Educational Attainment

of Mother,” to years of schooling. In this study,

the mother’s educational attainment is used as

an indication of her socioeconomic status and is,

therefore, taken into account in analyzing the

association between the incidence of low birth

weight and the time of initiation of prenatal

cafe.

Age of mother. –The proportion of lowbirth-weight babies was lower when prenatal

care was initiated early by white mothers of all

ages, but the pattern was less clear for black

infants (table O). For each age group, a substantial part of the difference can be explained by

the higher educational attainment of mothers

who started prenatal care earl y in the pregnancy.

After adjustment for variations in years of

education, there was only a 10-percent elevation

in the incidence of low birth weight among

children of white mothers (all ages combined)

who started care in the last trimester rather than

in the first 2 months of pregnancy. Before

adjustment, this difference was 27 percent. For

black infants, adjustment resulted in an incidence of low birth weight 3 percent lower when

care started late rather than early. Before adjustment the proportion was 3 percent higher for

late care.

As shown in table 4, as years of education

increased for all age groups of mothers except

teenagers (many of whom had not had the

opportunity to complete their education), the

incidence of low birth weight generally decreased, regardless of when prenatal care began.

The proportion of infants of low birth weight

born to white mothers declined from 8.6 percent for mothers with O-8 years of education to

4.5 percent for mothers who had completed 16

or more years of education. For black infants

the comparable decline was from 14.8 percent

to 9.5 percent. However, for each age group and

at all educational levels, the percent Iow birth

weight was far higher when mothers had no

prenatal care than when some care was received.

15
Table O. Observed and adjusted percent of infants of low birth weight by age of mother, month of pregnancy prenatal care began, end

race of child: Total of 41 reporting States and the District of Columbia, 1976

5’”All races . ................ “ ‘ “‘“”’mother

k

Ist and 2d month .................... 6.4

3d month................................. 6.9

4th.6th month .. ..... ...... ...... .. .... 8.7

7th.9th month ........ .. .. ...... ..... .. 8.6

NO prenatal caro . ... .. ...... .. ...... .. 23.0

White ............... ........ .. ...

w

1st and 2d month ...... ........... ... 5,6

3d month..., ............................. 5.9

4th,6th month .. ..... ....... .. ... ...... 7.1

7th-9th month ....... ... .. .. .. ... .. ... . 7.1

No prenatal care . ...... .. .. .. ....... .. 19.2

II Under 20 years I

20-29 years

AI 14’! ‘4”’!12”3

12.3 14.3 14.4 11,4

12.7 14.8 I 4.8 11.7

12.6 13.6 13.8 12,2

11.9 13.2 13.1 11.4

28.5 31.2 31.0 26.7

1 Adjusted for differences in mother’s educational attainment.

Zlnclude$ races other than white and black.

Adjusted 1

6.7

6.2

6.3

7.6

7.3

20.6

6.7

5.5

6.5

6.2

6.0

16.1

12.3

11.7

11.8

12.0

11.1

26.9

7.0 7.0 9.5 9.5

6.3 6.5 6.4 8.8

6.5 6.5 6.7 8.9

8.1 7.5 10.2 10.0

7.7 10.5 9.6

2::: 22.1 19.0 19.4

641 6.1 8,6 8,6

5.7 6.9 7.2 7.4

5.7 5.7 8.1 8.3

7.0 6.5 9.8 9.s

6.5 9.3 8.7

1:: 17.5 15.5 16.2

12.1 12.1

10.6 10.8

11.8 11.8

12.2 11.9

11.6 11.5

28.4 28.5

13.1 13.1

13.5 13.4

11.0 11.0

12,1 12.6

13.8 12.8

28.0 25.8

This persistent elevation can be explained in part out-of-wedlock infants (9.1 percent) than other

by the fact that the “no care” category is

heavily weighted with premature births, where

the mother delivered before having the opportunity to receive care.* 3

Mzn”tal status.–The incidence of low birth

weight among infants born to married mothers

increased with each delay in starting prenatal

care (table P). For white married mothers, the

proportion of infants of low birth weight was

5.4 percent when care started in the first 2

months of pregnancy and 6.8 percent when care

was delayed to the last 3 months. For black

married mothers, the comparable increase was

from 10.5 percent to 11.3 percent. However, the

risk of low birth weight declined for both white

and black infants born out of wedlock when

care was delayed. As noted in a previous

report, 13 this is partly due to the large numbers

of unmarried mothers who started care early but

delivered prematurely.

Regardless of when prenatal care began,

there was a higher risk of low birth weight

among out-of-wedlock than among other infants. When care began in the first 2 months of

pregnancy, the incidence of low birth weight

was more than two-thirds greater among white

white infants (5.4 percent) and more than

one-third higher among black out-of-we dlock

infants (14.2 percent) than other infants (10.5

percent). The differentials by marital status were

greatly reduced when care was delayed until the

second or third trimester of pregnancy.

Outcome of Last Pregnancy

and Birth Interval

Both the outcome of the previous pregnancy

and the interval since the termination of the

previous pregnancy are closely related to the

survival and birth weight of the current birth. In

a continuing study of approximately 59,000

pregnancies, it was found that if the mother’s

last pregnancy had terminated in a fetal or

neonatal death, her present infant had a greatly

increased risk of stillbirth, neonatal death, or

low birth weight.31 Those infants conceived

within 3 months and born within 1 year of a

previous full-term pregnancy had lower birth

weights on the average than a matched group of

infants born within 2-5 years of a previous

full-term pregnancy.32

As shown in table Q, there was a higher

incidence of low birth weight among both white

.

*

16
Table P. Percent of infants of low birth weight by month of Pre9nancY Prenatal care ba9an, marital status of mother, and race of child:

Total of 34 reporting States and the District of Columbia, 1976

Month of pregnancy prenatal care hgen

Marital status and race Total 1st and 3d 4th-6th 7th-9th ‘0 Not

2d month month month month prenatal stated

care

AH racesl .............................................................. 7.3 6.3 6.8 8.5 8.5 20.7 10.2

Births to married mothers ..................................................... 6.4 5.8 6.1 7.3 7.5 16.8 8.8

Births to unmarried mothers ................................................. 12.6 12.1 12.3 11.9 10.2 25.5 15.7

Whi~ .......................................................................... 6.1 5.5 5.8 6.9 7.1 16.8 8.6

Births to married mothers ..................................................... 5.8 5.4 5.6 6.6 6.8 14.9 8.1

Births to unmarried mothers ................................................. 9.7 9.1 9.2 9.1 8.0 20.8 13.6

Black .......................................................................... 13,0 11.9 12.6 12.9 12.4 29.2 15.3

Births to married mothers ..................................................... 11.2 10.5 10.9 11.3 11.3 26.0 13.3

Births to unmarried mothers ................................................. 14.7 14.2 14.4 13.9 13.0 30.7 17.0

lIncl~de~ races other th~ white and black.

Table Q. Percent of single-live-birth infants of low birth weight by outcome of last pregnancy, interval since termination of last

preg;ancy, and rata of child: Totel of 43 reporting States and the District of Columbia, 1976

Intewal since termination of last pregnancy and rata

All rWe#,2

..................................................................................................

Lessthan 12 months ....................................................................................................

12-23 months ...............................................................................................................

24-35 months ...............................................................................................................

36-47 months ...............................................................................................................

48 months and owr ......................................................................................................

Not stated ....................................................................................................................

White2 ...............................................................................................................

Lessthan 12 months ....................................................................................................

12-23 months .......................................................................................................... ....

24-35 months ...............................................................................................................

36-47 months ...............................................................................................................

48 months and over................................................................................................$.....

Not stated ....................................................................................................................

Black2 ...............................................................................................................

Lassthan 12 months ....................................................................................................

12-23 months ...............................................................................................................

24-35 months ...............................................................................................................

3647 months ................................................. .............................................................

48 months and owr ......................................................................................................

Not stated ....................................................................................................................

lIncludes races other than white and black.

21ncludes SII single live births resulting from second and higher order pregnancies.

Total

5.9

14.9

6.2

4.7

‘4.6

5.3

8.2

4.B

12.1

5.0

3.9

3.8

4.5

6.5

11.5

25.6

12.1

9.8

9.5

1Yo

Last

pregnancy

Iive

birth

5.4

17.8

6.1

4.4

4.4

5.2

6.6

4.4

14.5

4.8

3.7

3.6

4.3

5.1

10.6

26.5

11.8

9.3

9.2

9.1

12.6

Last

pregnancy

fetal

death

8.5

11.7

6.9

8.0

8.2

9.0

10.5

7.1

9.8

5.8

6,8

7.2

7.5

8.8

15.7

23.8

13.9

14.2

13.6

16.2

16.4

Last

pregnancy

outcome

unknown

8.6

27.3

8.4

6.1

9.2

7.8

8.6

6.8

●35.3

8.2

5.7

9.6

7.9

6.8

14.1

8.6

●11.8

8.3

14.1

17
and black infants in single deliveries when the

last pregnancy resulted in a fetal death rather

than a live birth.c For all races combined, the

proportion of infants of Iow birth weight among

current births was 8.5 percent when the last

pregnancy was a fetal death and 5.4 percent

when the last delivery was a live birth (an

increase in risk of 57 percent).

Mothers were least likely to bear a lowbirth-weight baby when the interval between

births was 2-4 years. The incidence of low birth

weight for this interval was between 4.6 percent

and 4.7 percent. Both shorter and longer intervals were associated with an increase in the

proportion of low-birth-weight babies. When the

current birth was within a year of the previous

delivery, the proportion of infants of low birth

cThe analysis of the risk of low birth weight in this

section is based on data that exclude multiple births.

weight increased to 14.9 percent, more than 3

times the proportion of low-birth-weight infants

for intervals of 2-4 years.

The age of the mother and the interval

bet ween births were related. For example, in

1976, 23 percent of the mothers delivering

within 1 “year of a previous live birth were less

than 20 years of age; only 3 percent were 35

years or more. As noted in “Age of Mother,” the

incidence of low birth weight varied with the

mother’s age. However, within each age group

there was a large variation in the proportion of

low-birth-weight babies according to the length

of the interval between births (table R). The

same pattern of a higher incidence of Iow birth .

weight for very short and very long intervals and

an optimum interval of between 2 and 4 years is

evident for each age group.

The distribution of low-birth-weight and .

heavier babies by interval since termination of

Table R. Percent of single-live-birth infants of low birth weight, by age of mothar, interval since last live birth, and rata of child: Total

of 43 reporting States and the District of Columbia, 1976

Intervalsince last live birth and race Total

All races1~2 . ..... ....... ..... ................................. ................. . 5.7

Less than 12 months .......... .... ........ ...... ...... ...... ..... ......................... 18.2

12-23 months ............................................. ........................... ...... ... 6.3

24-35 months ...................... ............ ........................... ...... .... ........ .. 4.7

36-47 months .. .............. .................. ................... .. ...... ............ ........ 4.6

48 months and over ............................... .. ............................. ......... 5.6

Not stated .. ................. ....... ....................... ...... ............ ...... ...... .. ..... 7.2

White* ................................................................................. 4.6

Less than 12 months ......................... .......... ..... ............ .. ...... .......... 14.8

12-23 month s.:........................ ........ ............. ............ ............ .......... 5.0

24-35 months ................ .................. .... ........ ....... ................... ......... 3.9

36-47 months ............. ........... ...... ............ ........... .. .... .. ............ .. .... .. 3.8

48 months and over .............. ..... ............ ......... .... ...... ...... ............... 4.7

Not stated ........... ........................................................... .. .............. 5.6

Black* ....... ........ ........................ ............ .... .............. .. ...... .... 11.0

Less than 12 months ......... ................... ............ .............. .... ........ .... 26.9

12-23 months ......... ...... ................................ .. .. ...... .... .. .. ........... ... .. 12.1

24-35 months ............................. ............. ..... ..... ............. ...... .. ........ 9.9

36-47 months ............................. ..... ...... ........ .... ...... .............. ...... ... 9.7

48 months and over ............. ...... ............ ........... ............... ..... ........ . 9.8

Not stated ........ ...................... .......... ............. .................... .... ......... 13.1

Aga of mother

Undar

20 years

10.7

25.6

10.2

8.3

8.6

9.3

13.4

8.1

20.6

7.9

6.2

6.1

6.5

9.1

15.3

33.6

14.8

12.2

12.3

12.1

19.8

20-24

years

6.1

17.5

6.4

5.1

5.3

6.1

7.9

4.8

14.7

5.2

4.1

4.2

4.7

6.2

11.2

24.3

11.7

10.1

10.0

10.5

12.9

25-28

years

4.6

14.2

4.7

3.8

3.8

5.0

5.7

3.9

11.8

3.9

3.4

3.3

4.2

4.5

9.5

24.3

10.0

8.4

8.7

9.1

11.6

30-34

years

5.0

13.1

5.1

3.8

4.2

5.3

6.4

4.4

11.5

4.4

3.3

3.7

4.7

5.4

9.4

18.8

9.8

8.2

8.6

9.3

11.1

35-39

years

6.4

14.8

5.7

5.2

5.2

6.8

8.1

5.6

12.5

5.0

4.7

4.4

5.9

7.2

10.8

22.8

9.6

8.1

10.2

11.3

10.9

40 years

and over

8.0

22.5

6.8

6.5

6.2

8.4

8.4 ,

7.2

16.7

4.9 .

6.2

5.6

7.8

5.1

11.8

38.7

12.9

8.5

9.0

11.3

17.9

1[ncI”des races other than white and black.

*Includes aH single Iive births resulting from second and higher order pregnancies.

18
.

.

last pregnancy is shown in table S. There was a

higher concentration of low-birth-weight babies

at the shorter interbirth intervals-39.1 percent

of all low-birth-weight babies were born within 2

years of the termination of the previous pregnancy, compared with 30.2 percent of the

higher weight babies. Nearly 3 times the proportion of low-birth-weight than other babies were

born within a year of the previous delivery (8.3

percent compared with 2.8 percent). Similar

differences were found for each race. The mean

interval between births was Y2 month shorter for

white infants of low birth weight than white

heavier babies and 4 months shorter for black

infants of low birth weight than other black

babies.

The study of closely spaced pregnancies

cited earlier3z concluded that the depression in

Table S. Percent distribution of single live births by interval

since termination of last pregnancy, according to race of

child and birth weight: Total of 43 reportirw States and the

District of Columbia, 1976

Interval sinca termination

of last pregnancy and race

All racesl ........... .........

Less than 12 months .,, ..... .... .......

12-23 months .......................... ....

24-36 months ..............................

36-47 months ..............................

48 months and ovar ............ ........

Mean interval in months2 ............

White ........................... .....

●

Less than 12 months ...................

12-23 months .................. ...........

24-35 months ..... .........................

36-47 months... .............. ............

. 48 months and over ............ .... ....

Maan interval in months . ......... ..

Black ........................ .......

Less than 12 months .. ..... ............

12-23 months .............. ........... .....

24-35 months ........ ...... ...... .. .... ....

36-47 months . ........ .....................

48 months and over ....... ............ .

Mean intewal in months . ...........

Total

100.0

3.1

27.6

23.0

15.6

30.7

41.8

100.0

2.9

27.1

23.7

160

30.4

41.7

100.0

4.0

29.8

19.6

13.8

32.8

42.8

Birth weight

2,50(

gram:

or Ies

loos

8’

30:;

19.:

12.7

29.C

40.6

I 00.0

7.7

29.7

20.1

13.0

29.5

41.2

100.0

9.4

33.0

17.5

11.9

28.1

39.3

2,501

grams

or more

100.0

2.8

27.4

23.2

15.8

30.8

41.9

100.0

2.7

26.9

23.8

16.1

30.4

41.7

100.0

3.4

29.4

19.9

14.0

33.4

43.3

lIncludes races other than white and black.

zln~[udes all single live births resulting from second snd higher

order pregnancies.

birth weight associated with these pregnancies

could not be attributed to social class differences or prematurityy, since these factors had

been controlled. Rather, it appeared probable

that fetal growth was stunted because the

mother had insufficient time between pregnancies to restore supplies of nutrients critical for

optimum fetal body development.

GEOGRAPHIC VARIATIONS

There are relatively large differences in the

incidence of low birth weight according to

mother’s pIace of residence. As shown in table 5,

the proportion of low-birth-weight babies was

highest in the South Region (8.0 percent) and

lowest in the West Region (6.4 percent). However, part of the overall difference among

regions was due to variations in the proportion

of black infants born in each region. For

example, 25 percent of the infants born in the

South Region were black, but only 7 percent of

those born in the West Region were black.

Considering each racial group separately,

there was still considerable variation by geographic area in the incidence of low birth weight.

Among States, the lowest incidence for white

infants was in North Dakota (4.9 percent) and

the highest was in Colorado and Wyoming (8.5

percent). The proportion of low-birth-weight,

black infants ranged from 1.7 percent in Idaho

to 17.2 percent in Wyoming. However, in both

States, there were fewer than 100 black infants

born during 1976. If States with less than 100

black births are excluded from the comparison,

there is approximately the same degree of

variation in the incidence of low birth weight

among States for each racial group. The coef ficient of variation of the percent low birth

weight among States was 11.1 percent for white

infants and 9.6 percent for black infants.

Within States, the incidence of low birth

weight for infants of races other than white or

black was generally higher than that for white

infants but substantially lower than that for

black infants (table 5). However, when interpreting these data, it should be borne in mind

that the category “other races” includes a wide

diversity of racial and ethnic groups (see appendix II) with varying representation from State to

State.

19
Two factors known to be associated with a

high incidence of low birth weight are low

educational attainment and teenage motherhood. However, variations from State to State in

the proportion of mothers who had less than 12

years of education or who were teenagers

accounted for only 13 percent of the total

variation in the proportion of low-birth-weight

white babies and 10 percent of the total

variation among black babies.

Both white and black mothers living in large

urban places were more likely than mothers

residing in very small urban places to bear a

low-birth-weight baby (table T). The incidence

of low birth weight decreased progressively as

size of place decreased, from 7.2 percent for

infants born to white mothers residing in cities

of 1,000,000 or more population to 6:2 pcrccnt

for infants born to white mothers residing in

cities of 10,000 to 50,000 population. The

comparable decrease in incidence for infants

born to black mothers was from 14.1 percent to

12.8 percent. An even lower incidence was seen

for infants born to mothers living in the remaining, primarily rural, areas (5.9 percent and 12.1

percent for white and black infants, respectively). The decline in the incidence of low birth

weight with decreasing size of place can be observed at each level of educational attainment,

an indication that factors other than years of

education are responsible for these differences. .

Table T. Percent of infants of low birth weight by educational attainment of mother. siza of place of residence. and race of child: Total

of 44 reporting States and the District of Columbia, 1976

8ize of Place of rasidence and race

All racesl ...................... ........ ............... .............. .............. ................... ................. .......

Urban pIaces ...................... ...... ............ .............. ... .................. .................... .............. .... ..............

1,000,000 or more population ................ .... ............. ... ..................... ...... ... ..... .... ....... .............

500,000-1,000,000 population .............. ...... .... .. .... ....... ............................................ ...... ...... .

100,000.500,000 population ........... ...... ............ ..... .......................... ........ ...... ................ .. .....

50,000-100,000 population ............ ......! ...... .. .... ...... ........ .................. ...... .................. ........ ....

10,000-50,000 population ............... .................... ............ .......... .... .. .... .... ...... ...... ............ .. ....

Balance of area ................... ............ ......................... ...... ............ .................... .. .... ...... ..................

White .. ......... ...... .................................................... .................... ................ .......................

Urban places ................................................ .... .... .......... .... ........................................ ........ .........

1,000,000 or more population ................ ...... .. ..... ............ ..... ....... ...... ............ .. .... .. ................

500,000-1,000,000 population ...................... .... .. .... .. ........... ....... .. .. ................ .......4.... .. ...... ..

100,000-500,000 population ............... ........... .... ........ ...... .......................... .......... .................

50,000190,000 population ........................... ............ ...... .............. ............. ...... ........ ...... ...... .

10,00050,000 population .... ............ ........................ ............................. ............ ...... ............ ..

Balance of area ................................................................... .... .................... .................. .. ...... .......

Black .................... ............ ..................... ............................. ....... ............ .. ............ .............

Urban places ............ .................. ...... ............................................... ........................ ....... .............

1,000,000 or more population .......... .............. .............................. .... ......... ................ ...... ......

500,000-1,000,000 population ................. ...... ...... ...... .................. .. ...... .. .... .................... .. .... .

100,000-500,000 population . ....... .............. .......... .... .. ...... ............................ .................. .......

50,000-100,000 population ....................... .... ...... ...... ........ ...................... .................. ...... ......

10,000-50,000 population ........... .............. .. .. .. ...... .... ...... ................ .......... .. .. ...... ...... ............

Balance of area ........ ........ .......................... ........... ........... .. .................... ...... ........ ...... .... .. ...... ......

Total

7.4

8.3

10.2

9.6

8.6

7.4

7.0

6.6

6.2

6.5

K

6.6

6.3

6.2

5.9

13.1

13.5

14.1

13.5

13.3

13.4

12.8

12.1

Years of school completed

by mother

Less

than

12 years

10.1

11.1

12.1

11.8,

11.4

10.4

10.1

9.1

8.4

8.8

8.5

8.7

9.0

8.7

8.9

8.1

14.8

15.2

15.9

14.9

15.2

15.5

14.4

13.6

-

12

years

6.8

7.7

9.5

8.8

7.9

7.0

6.6

6.0

5.8

6.1

6.8

6.4

6.1

6.0

5.9

5.6

12.0

12.4

13.0

12.2

12.1

12.5

11.8

11.1

13 years

or more

5.5

6.0

8.0

7.1

6.3

5.5

5.2

5.0

4.9

5.0 ?.

5.9

5.5

5.1

5.0

4.8

4,7 A

10.7

11.0

11.5

11.2

11.1

10.3

10.5

9.5

llncl~ldes races other than white and black.

20
REFERENCES

.

“

I National Center for Health Statistics: A study of

infant mortality from linked records by birth weight,

period of gestation, and other variables, United States.

Vital and Health Statistics. Series 20-No. 12. DHEW

Pub. No. (HSM) 72-1055. Health Services and Mental

Health Administration. Washington. U.S. Governrnent

Printing Office, May 1972.

2Chase, H. C., and Nelson, F. G.: Education of

mother, medical care and condition of infant. Part 3 of a

study of risks, medical care, ‘and infant mortality. Am. ].

Public Health 63:27-40, Sept. 1973 Supp.

SNational Center for HeaIth Statistics: cOIWIdd

anomalies and birth injuries among live births, United

States, 1973-74, by S. Taffel. Vital and Health Statistics.

Series 21-No. 31. DHEW Pub. No. (PHS) 79-1909.

Public Health Service. Washington. U.S. Government

Printing Office, Nov. 1978.

4 Churchill, J. A., et d.: Birth weight and intelligence.

Obstet. Gynecol. 28(3):425-429, Sept. 1966.

5Wiener, G., et al.: Correlates of IOW birth weight.

Psychological status at eight to ten years of age. Ped@r.

Res. 2:110-118, March 1968.

6Lubchenco, L. O., et al.: Sequelae of premature

birth. Am. ]. Dis. Child. 106:101-115,JuIy 1963.

7placek, p. J.: MatemaI and infant health factors

associated with low infant birth weight: Findings from

the 1972 National Natality Survey, in D. M. Reed and F.

J. Stanley, eds., The Epidemiology of Prematurity.

Baltimore. Urban & Schwarzenberg, 1977. pp. 197-211.

8Rosenwaike, I.: The influence of socioeconomic

status on incidence of low birth weight. HSMHA HeaZth

Reperk. 86(7): 641-649, July 1971.

9Lechtig, A., et rd.: Effect of food supplementation

during pregnancy on birthweight. Ped{atn”cs

56(4):508-520, Oct. 1975.

1Owleiss, W., and Jackson, E. C.: Maternal factors

affecting birth weight, in Perinatal Factors Affect{ng

Human Development. Scientific Publication No. 185.

Washington, D.C. Pan American Health Organization,

Oct. 1969.

11 Little, R. E.: Moderate alcohol use during pregnancy and decreased infant birth weight. Am. j. Public

Health 67(12):11541156, Dec. 1977.

12 center for Disease Control: The he~th con~equences of smoking. DHEW Pub. No. (CDC) 78-8357.

Public Health Service, Atlanta, Ga. 1976.

13 National Center for He~t,b Statistics: prenat~ ~~e,

United States, 1969-1975, by S. Taffel. Vital and Health

Statistics. Series 21-No. 33. DHEW Pub. No. (PHS)

78-1911. Public Health Service. Washington. U.S. Government Printing Office, Sept. 1978.

14Newcombe, R., and Chalmers, I.: Changes in distribution of gestational age and birth weight among fwst

born infants of Cardiff residents. Br. Med. J. (2)925-926,

Oct. 8, 1977.

15 Berendes, H. W.: Methods of family planning and

the risk of low birthweight, in D. M. Reed and F. J.

Stanley, eds., The Epidemiology of Prematun.ty. Baltimore. Urban & Schwarzenberg, 1977. pp. 281-289.

16van den Berg, B. J., and Yerushahny, J.: The

relationship of the rate of intrauterine growth of infants

of low birth weight to mortality, morbidity, and

congenital anomalies. ]. Pediatr. 69(4)531-545, Oct.

1966.

17Yerushalmy, J.: The classification of newborn infants by birth weight and gestational age. J. Pediatr.

71(2):164172, Aug. 1967.

18 Bergner, L., and Susser, M. W.: Low birth weight

and prenatal nutrition: an interpretive review. Pedia tries

46(6):946-966, Dec. 1970.

19 Hendricks, C.: Delivery patterns and reproductive

efficiency among groups of differing socioeconomic

status and ethnic orgins. Am. J. Obstet. Gynecol.

97(5):608-624, Mar. I, 1967.

20 Placek, P. J.: Underlying medical conditions, complications of pregnancy, and complications of labor to

mothers of legitimate live hospital births in the United

States. Paper presented at the Population Association of

America meeting, Atlant~ Ga., Apr. 13-15, 1978.

21 Unpublisheddata from the National Center for

Health Statistics, Health and Nutrition Examination

Survey, 1971-74.

22 placek, P. J.: The relationship of social and demographic, maternal health, and infant health factors to

one and five minute Apgar scores: Findings from the

1972 National Natality Survey. Paper presented at the

104th American Public Health Association Annual Meetin , Miami Beach, Fla., Oct. 17-21, 1976.

#3 Placek, P. J.: Type of delivery associated with social

and demographic, maternal health, infant health, and

health insurance factors: Findings from the 1972 National Natality Survey. Paper presented at the American

Statistical Association Meeting, Chicago, Ill., Aug. 15-18,

1977.

24 Powers, W. F.: Twin pregnancy, complications and

treatment. Obstet. GynecoL 42(6):795-808, Dec. 1973.

25 Hendricks, C. H.: Twinning in relation to birth

weight, mortality, and congenital anomalies. (?bstet.

Gynecol. 27(1):47-53, Jan. 1966.

26McKeow, T., and Record, R. G.s obsemations on

foetal growth in multiple pregnancy in man. ~. Endocrinol. 8:386-401, 1952.

21
27 National Center for Health Statistics: Trends and

differentials in births to unmarried women, United

States, 1970-76, by S. J. Ventura. Vital and Health Statistics. Series 21-No. 36, Public Health Service, DHEW,

Hyattsville, Md. In preparation.

28 Berkov, B., and Sklar, J.: Does illegitimacy make a

difference? A study of the life chances of illegitimate

children in California. Popul. Dev. Rev. 2(2):201-217,

June 1976.

29 Schneider, J.: Low birth weight infants. Obstet.

GynecoL 31(2):283-287, Feb. 1968.

~ONational Center for Health Statistics: Selected vital

and health statistics in poverty and nonpoverty areas of

19 large cities–United States, 1969-71, by S. J. Ventura

et al. Vital and Health Statktics. Series 2 I-No. 26.

DHEW Pub. No. (HRA) 76-1904, Health Resources

Administration. Washington. U.S. Government Printing

Offjce, Nov. 1975.

31 Niswander, K. R., et al.: The Women and Their

Pregnancies. The Collaborative Perinatal Study of the

National Institute of Neurological Disewes and Stroke.

DHEW Pub. No. (NIH) 73-379. U.S. Dept. of Health,

Education, and Welfare. Washington. U.S. Government

Printing Office, 1972,

S2Holley, W. L., et al.: Effect of rapid succession of

pregnancy, in Pert”natal Factors Affecthg Human Develo$men t. Scientific Publication No. 185. Washington,

D.C. Pan American Herdth Organization, Oct. 1969.

33 National Center for Health Statistics: Comparability

of reporting between the birth certificate and the

National Natality Survey, by L. J. Querec. Vital and

HeaZth Statistics. Series 2-No. 83. Public Health Service,

DHEW, Hyattsville, Md. In preparation.

22
LIST OF DETAILED TABLES

1. Percent of infents of low birth weight by race: United Stetes, 1950-76 ....................................................................................... 24

2. Percent of infants of low birth weight by period of gestation and race: Total of 42 reporting States and tha District of Columbia, 1976 ..................................................................................................................................................................................... 25

3. Parcent of infants of low birth weight by period of gestation, plurality of birth, and race: Total of 42 reporting States and the

District of Columbia, 1976 .................................................................................................................. . . . . . . . . . . ...s. ......................... 26

4. Percent of infents of low birth waight by educational attainment of mothar, age of mother, month of pregnancy prenatal care

began, and race of child: Total of 41 raporting Statas and the District of Columbia, 1976 .......................................................... 27

5. Percent of infants of low birth weight by reca: Unitad States, each region, geographic division, and State, 1976 ........................ 30

23
Table 1. Percent of infants of low birth weight by race: United States, 1959-76

Year

1959 ......................................................................................................................................... ........

19582 ...............................................................................................................................................

19572 ......................................................................................................................................... ......

19s2 ...............................................................................................................................................

19552~3

l9M2*3::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

1951213 ................................................................................................................................. ...........

1950213 ............................................................................................................................................

All

races

7.3

7.4

7.4

7.6

7.7

7.7

7.9

8.1

8.2

8.2

8.3-

8.3

8.2

8.2

8.0

7.8

7.7

7.7

7.7

7.6

7.5

7.6

7.4

7.6

7.6

7.5

7.5

rVhite

6.1

6.3

6.3

6.4

6.5

6.6

6.8

7.0

7.1

7.1

7.2

7.2

7.1

7.1

7.0

6.9

6.8

6.8

6.8

6.8

6,7

6.8

6.8

7.0

7.0

7.0

7.1

All other races

Total

12.1

12.2

12.4

12.5

12.9

12.7

13.3

13.5

13.7

13.6

13.9

13.8

13.9

13.6

13.1

13.0

12.8

12.9

12.9

12.4

12.0

11.7

11.3

11.3

11.1

10.7

10.2

Black

13.0

13.1

13.1

13.3

13.6

13.4

13.9

14.1

. . .

. . .

. . .

-..

---

. . .

. . .

. . .

. . .

. . .

..-

.-.

.-.

. . .

. . .

. . .

. . .

. . .

. . .

.

.

1Figures by color exclude data for residents of New J ersw.

2Excludes data for Massachusetts.

3&cludes data for cOIISXCtiCUL

.
Table 2. Percent of infants of low birth weight by period of wtation and ram To@+l of 42 rePOrtin9 states and the District Of

.

.

Columbia, 1976

Period of gestation

Total ................................................................................................................................... ............

Under 20 weeks ................................................................................................................................. .............

20 wks .........................................................................................................................................................

21 weks .........................................................................................................................................................

22 mks .........................................................................................................................................................

23 waks ............................................................................................................................................ .............

24 mks .........................................................................................................................................................

25, weeks.........................................................................................................................................................

26 weks ................................................................................................................................... ......................

27 wks .........................................................................................................................................................

28 weaks.................................................................................................................................. .................... ...

29 weeks...................................................................................................................................... ...................

30 waaks.........................................................................................................................................................

31 weks .........................................................................................................................................................

32 weks .........................................................................................................................................................

33 ~eks .........................................................................................................................................................

34 wh .........................................................................................................................................................

35 weeks.................................................................................................................................... .....................

36 reeks .........................................................................................................................................................

37 weeks.................................................................................................................................. .......................

38 reeks .........................................................................................................................................................

39 wb ................................c........................................................................................................................

40 weeks.................................................................................................................................. .......................

41 weks .........................................................................................................................................................

42 weks .........................................................................................................................................................

43 weeks.......................................................................................................................................... ...............

44 *eks .........................................................................................................................................................

45 ~eks .........................................................................................................................................................

46 weeks..................................................................................................................................... ....................

47 weks .........................................................................................................................................................

48 waaks..................................................................................................................................... ....................

49 reeks .........................................................................................................................................................

50 weeks and over ................................................................................................................................... .......

Not stared.......................................................................................................................................................

1Includesracesotherthan fiite and black.

z

All White racasl

7.3 6.1

56.8

77.1

80.5

66.7

85.6

84.7

85.0

60.5

80.5

78.5

75.5

69.6

67.0

63.0

55.5

45.0

32.2

21.7

12.7

6.4

3.3

2.1

1.7

1.6

2.1

2.5

2.4

2.6

3.1

3.0

3.5

4.4

9.2

50.7

75.3

79.0

84.4

8!5.6

84.9

85.3

83.7

82.4

81.4

78.1

71.4

70.1

65.8

58.3

47.5

32.6

21.0

12.0

5.8

2.9

1.8

1.4

1.3

1.7

2.1

1.9

2.1

27

2.6

2.7

3.5

7.5

Black

12.9

65.7

78.9

82.3

90.2

85.6

84.0

84.4

75.5

76.9

73.5

70.8

67.4

61.8

57.6

50.5

39.9

31.5

23.8

15.6

9.2

5.6

4.1

3.9

4.1

5.0

4.9

4.8

5.6

5.6

4.7

8.8

9.0

15.1

.
Table 3. Percent of infants of low birth weight by period of gastation, plurality of ‘birth, and race: Total of 42 reporting States end the

District of Columbia, 1976

Period of gestation

Plurality and race Total 1

20-27 28-31 32.35 36 37-39 40 41-42 43 weeks Not

vmeks weaks waa ks wee ks weeks waaks waaks and over stated

All racas2 ........................... 7,3 82.6 71.3 43.3 21.7 5.6 2.1 1.7 2.4 9,2

Single live births ................................. 6,3 80,2 67.7 39.2 18,9 4.9 1.9 1.s 2.2 “ 8.2

Liva births in plural dallverlas.,,,,, ....... 64,2 97.8 97.7 64.7 61.7 36.5 26.1 26.9 32.6 59.8

White ....................................... 6.1 83.5 73.9 44.7 21.0 5.0 1.8 1.4 , 2.0 7,6

Single live births ,...,..,,..,..!,,,. .............. 5.2 80.7 70,1 40.1 18.1 4.3 1.2

Liva births in plural deliveries.., .......... 51,6 98.2 98,8 84.6 60.1 34.2 2E 24,3 3;; $:

Black ....................................... 12,9 81.2 67.1 40.6 23.8 8.6 4.1 4.0 6.2 15,1 .

Single Iiva births .,..........!...... ,,.,......!,,. 11.7 79.3 64.1 37.7 21.5 7.8 4,8 13.8

Live births in plural deliveries..., ......... 84,0 98,1 95.1 85.3 66.4 46.6 3?: 3::: 39,4 68.7

1In~l~d~~livebi~thaOf less than 20 w~e~) gesfati~~. .

%cludes races other than white and black.

26
Table 4. Percent of infants of low birth weight by educational attainment of m-other, age of mother, month of pregnancy prenatal care

began, and race of child: Total of 41 reporting States and the District of Columbia, 1976

Age of mother, month of pregnancy

prenatal care began and race

All races 1

All ages ................ ........... ............ ..... ..... ..... ..................... .......

1st-2d month ................... ................ ......................................................

3d month .... ........................... ..................... ...........................................

4th-6th month ............. ............................... ...... ............................... .. ....

7th-9th month ....... ............ ................................. ...... .... .........................

No prenatal care ......................... ...... ........ ..................... ...................... ..

Not stated .................................... ................. ....... ..................................

*

Under 20 years ..... .................................................... ............ .......

1st-2d month ................................................................... ......................

3d month .......... .... ....................... .......... ............ .... .......... ...... ...... .... ......

. 4th-8th month . ................. .... ............................. ...... ........................ ......

7th-9th month ....................................... ..... ......... ............. ..... .............. ..

No prenatal care .......... ..... ................ ..... ......... .......... ........ .. ...................

Not stated .... ............................................. .......... ............... ....................

20-29 years ............... ... .. ....................... .... .................... ..............

1st-2d month ...... ..... ........................ ................ ........... ......... ..... ............ .

3d month . ................... ... ........... ....................... .. .. ... .... ...........................

4th-8th month ..... .. ...... ..... ... ............................ ................................ ......

7th-9th month .......... ....................... ............ .................... .......... ............

No prenatal care .............. ................. .... ..... ....................... .....................

Not stated ... ................ ........................... ............ .... ................................

30-39 years ....................... ........... .. .... .. .............................. .... .... .

1st-2d month ........ ....... ...... ................... ............... .............. ....................

3d month ... ....................... ............ .......... .................. .... ........ ................ .

4th-6th month ............. .... .. ......... ............................................. .. ..... .......

7th-9th month .................. ................ ........ .......... ..... ......................... .....

No prenatal care .... .......... ........ ............ .. .. ........ .... ...... .......... ............ ......

Not stated ............. .......... ................ ...... .................... .. .... ...... ...... ..... ......

.

40 years and over .... .... ........................ ................. ..... ............ .....

1st-2d month ........................................ ...... ................ ...........................

3d month ................. ...... ............................... .... ...................... ...............

4th-6th month ................... ............... ............................. ................. ......

. 7th-9th month ............. ........ ........ ....... ................ ...... ...... .... ................ ...

No prenatal care ..... ..... ........................ ...... ....................... .. ............ .......

Not stated ..................... ............................ .................................. ...........

White

All ages ................. .... ....... ......... ....... ...... ...... ... .. .......... ..... ......

1st-2d month ......... ............... ...... ................ .. .............. ...........................

3d month ..................... .... ........... ...................... ..................... ............ ....

4th-6th month ....... .......... .. .... ........... ............. ....... ...... ...... ................... ..

7th-9th month ............. ...... ................ .... ........ ....... .. .......... .............. .......

No prenatal care ..... .......... ........................ ...... ..... .............. .............. ......

Not stated ............... ................................. ............. ..... .............. .. ............

See footnote at end of table.

Tots!

7.4

6.4

6.9

8.7

8.6

23.0

10.6

10.3

9.0

9.7

10.1

9.7

27.2

14.1

6.7

6.0

6.3

7.9

7.9

20.5

9.5

7.0

6.3

6.5

8.1

8.3

21.8

9.7

9.5

8.4

8.7

10.2

10.5

19.0

12.2

6.2

5.6

5.9

7.1

7.1

19.2

8.7,

0-8

year<

9.9

8.6

9.7

9.7

9.3

22.0

12.8

12.4

10.7

11.9

11.7

11.3

2&8

16.8

8.6

7.7

8.7

8.3

8.0

19.5

10.3

9.0

8.0

8.7

9.2

7.9

17.6

12.2

10.3

10.2

10.3

9.9

10.7

12.6

11.5

8.6

7.7

8.6

8.2

8.3

19.2

10.7

Vs...-+..4.,.-1 -“”-. -!.-. +,..4 1..., -.-.. L....

. =-.= w! au,,””, G“, ,,p, GL=” “y ,, ,”,,,=,

8-11

years

10.2

9.2

9.5

10.4

9.8

24.2

13.6

10.9

10.0

10.4

10.6

9.9

27.0

14.7

9.4

8.5

8.7

10.0

9.5

21.0

12.6

10.3

9.5

9.3

10.9

10.6

23.4

13.6

12.0

12.5

11.3

11.1

12.7

21.3

13.5

8.4

7.8

7.9

8.6

8.1

20.8

11.4

12

years

6.8

6.1

6.5

7.8

7.6

21.9

9.4

8.5

7.5

8.1

8.6

8.4

26.5

11.9

6.4

5.9

6.1

7.5

7.4

19.9

9.0

7.0

6.5

6.8

7.8

7.3

23.1

9.1

8.8

7.1

7.8

10.9

10.8

23.5

11.1

5.8

5.4

5.6

6.4

6.3

18.0

7.8

13-15

years

5.9

5.5

5.6

6.9

7.0

20.6

9.7

8.9

7.4

9.7

8.9

8.2

20.1

13.5

5.8

5.4

5.4

6.8

6.6

20.8

9.6

6.1

5.8

5.6

6.6

8.2

20.9

9.4

8.2

8.3

8.3

6.6

8,4

14.3

12.9

5.1

4.9

4.9

5.7

5.6

14.7

8.5

16 years

or more

4.9

4.9

4.5

5.4

5.3

21.1

7.0

14.4

7.1

10.7

19.4

●37.5

4.9

4.9

4.5

5.3

4.9

21.4

7.0

5.0

5.0

4.5

5.4

6.1

21.5

6.8

6.7

6.5

6.3

6.9

●13.3

14.6

4.5

4.6

4.0

4.8

4.1

17.8

6.6

Not

9.9

7.9

9.3

10.9

9.8

27.9

10.0

13.2

10.3

13.0

11.4

10.2

32.0

14.2

9.1

8.0

8.5

11.0

9.2

24.9

8.7

8.8

6.4

8.3

9.1

11.0

27,9

9.7

12.8

8.5

10.0

17.4

7.4

38.1

11.8

7.7

6.8

7.1

8.5

7.9

20.9

7.9

27
Table 4. Percent of infants of low birth weight by educational attainment of mother, age of mother, month of pregnancy pranatal cara

began, and rata of child: Total of 41 reporting States and the District of Columbia, 1976–Con.

Age of mother, month of pregnancy

prenatal care began and race

White-Con.

Under 20 years ................................................... .......................

1st-2d month ......... ............. ................................. ............ .....................

3d month ... ...... ..................... .......................... .......... ............................

4th-6th month ......... ....... ................................. .... .. .. .. .. .. .... ...................

7th-9th month ........... .. ......... ........................................... ............... ......

No prenatal cara ................... .......... ...... ............................................ooc..

Not stated .................. ...... .... ......................... .... ...... .... .. .. .... ...... ...... ..e... .

20-29 years ................... ......... .... ....... ........ .......... .... .. .. .......... ..... .

lst-2d month ... ...... .................................. .............................. ..........4.....

3d month ................................................................... ................ ............

4th-6th month ....................................................................... ................

7th-9th month ............ ......................................... .. .... .. .. .. ...... .... ...... .. ....

No prenatal care ................... ................... ........ ..... ..... ....... ....... .......... ....

Not stawd ............ ............ ..... ......... ........................ .... ...... .............. ........

30-39 years ..................................... ........... ............................... ..

1st-2d month ..... ............. .................................................... ...................

3d month ............ ........ .. .. .. ................................ .................................... .

4th-6th month ....................... .................... ................... .................. .......

7th-9th month ........................ ......... ........... ............. ....... .......................

No prenatal care ............... .................................. ............................ .......

Not xatad ..............................................................................................

40 years and over ............ .................. ............ .................. ...... ......

lst-2d month ...................... .............. .............. ...... .. .. ...... .......... .. ..... ..... .

3d month .......... ........................................................ .. .. .............. .... .. .....

4th-6th month ................................. .............. ...... ..................................

7th-9th month ...................... ............ .. .......... ........ .............................. ...

No pranatal care .... ........ ..................... ...................... .... .... .....................

Not stated ........................ ..... .............. ...................................................

Black

All ages ..... ............ ........................... ................ ...... ........ ....... .

lst-2d month ............. ............. ............................................................. ..

3d month ............................... ..... .......... ...... ............. .... ............. .............

4th-6th monti ... ....... ....... .. ...................................................... ........ .... ..

7th-9th month ... ........ ............. ............... ........... ..... ........ ... .....................

No prenatal care ................ ........... .................... ...... ........................ ...... .

Not stated ........... ..... ........ .................... ...... .............. ...................... .. .....

Under 20 years ............................................. ................ ..............

lst-2d month .................... ........................... ...... .. .... ...... ...... .... .. ............

3d month .............. ..... ................................ ........ ............ .... .. ..................

4th-6th month ............................................ ........ ...................... ........ .....

7th-9th month ....... ........................ ........................................................

No prenatal care ......... ...... .. ........................ ...... ..... ........... ......... ....... .....

Not stated ...... .......................................................... ............ ...... ...... ......

Tota

.!?.i

7.i

7..!

8.;

7.E

24.3

11.:

5.7

5.3

:::

6.7

16.4

7.8

6.1

5.7

5.7

7.0

7.1

1B.O

B.2

8.5

;::

9.8

9.3

1!3.5

11.3

13.1

11.9

12.6

12.8

12.2

28.6

15.8

14.9

14.3

14.8

13.8

13.2

31.2

17.7

0-8

years

10.6

9.3

10.6

9.8

10.0

26.1

12.7

7.6

7.1

7.7

7.2

7.4

16.2

8.9

8.0

7.3

7.7

7.6

7.4

16.2

11.6

9.7

7.9

10.7

9,9

7.2

14.0

12.3

14.8

13.1

14.3

14.2

13.0

31.4

19.8

16.8

15.3

15.6

15.8

13.9

35.1

25.7

v-... -6 . . .. L-... .-—_,.. - JL. .—-.L.

9-11

years

8.7

8.0

8.3

8.6

7.8

24.1

12.6

7.9

7.4

E

8.2

17.0

10.3

9.2

8.8

8,4

9.5

8.9

21.1

11.4

11.3

9.8

11.1

11.7

14.0

15.1

13.6

14.7

14,1

14.1

13.9

13.4

28.7

17.7

15.4

15.1

15.4

14.2

13.8

30.9

18.0

12

years

6.7

6.0

6.6

::;

23.3

10.7

5.5

5.3

5.4

6.2

6.1

16.3

7.3

6.3

R

6.8

6.5

17.4

7.9

8.0

6.6

6.8

10.3

10.8

18.0

9.4

12.0

11,3

11.7

11.9

10.8

26.7

14.0

13.2

13.1

13.1

12.5

11.6

30.3

14.1

13-15

years

6.6

5.5

6.7

6.6

6.8

18.8

9.4

5.0

4.8

4.8

5.5

5.3

13.7

8.4

5.5

5.3

5,2

6.1

IE

B.5

7.5

7,1

8.4

6.5

7.0

● 20.0

9.6

11.3

10,9

10.8

11.0

10.2

28.6

14.2

12.5

11.2

15.1

11.3

10.0

22.1

17.4

16 yaar!

or mora

13.2

10.5

9.5

15.0

●33.3

4.5

4.6

4.0

4.8

3.6

18.0

6.8

4.6

4.6

4.0

4.8

5.2

17.9

5.9

6.2

6.0

6.1

5.5

●14.3

16.7

9.5

8,8

10.4

9.1

11.1

32.3

10.2

20.0

●20.O

● 30.0

● 50.0

Not

statad

10.6

9.3

10.0

9.1

7.5

27.7

11.5

7.2

6.B

6.7

8.0 .

7.9

17.7

7.1

7.1

u,

8.5

9.1.

21.1

7.7

10.1

‘10.9

8.8

14.7

●5.6

8.6

16.2

14.0

15.5

15.3

.

13.1

36.1

16.4

16.9

12.7

16.5

14.3

13.8

35.5

18.1

See footnote at end of table.

28
Table 4. Percent of infants of low birth weight by educational attainment of mother, age of mothar, month of pregnancy prenatal cara

began, and race of child: Total of 41 raporting States and the District of Columbia, 1976-Con.

Age of mothar, month of pregnancy

prenatal ctwe began and race

Black-Con.

20-29 years ................................................................................

1st-2d month .........................................................................................

3d month ...............................................................................................

4th-6th month .......................................................................................

7th-9th month .......................................................................................

No prenatal cara

,

....................................................................................

Not stated..............................................................................................

30.39 years ................................................................................#

1st-2d month .........................................................................................

. 3d month .........................................................................*...... ...............

4th-6th month .......................................................................................

7th-9th month .......................................................................................

No prenatal cara ....................................................................................

Not stated..............................................................................................

1st-2d month .........................................................................................

3d month ...............................................................................................

4th%th month .......................................................................................

7th-9th month .......................................................................................

No prenatal care ....................................................................................

Not stated..............................................................................................

lln~ludes ~ace~other ~an fiita and black

Total

12.3

11.4

11.7

12.2

11.4

26.7

14.8

12.1

10.6

11.8

12.2

11.6

28.4

15.0

13.1

13.5

11.0

12.1

13.8

28.0

15.5

II Years of school completed by mother

@8

years

13.7

12.1

14.2

12.6

11.9

31.7

15.9

13.0

11.2

12.6

13.6

11.0

24.7

15.3

13.1

15.8

9.8

10.7

22.8

15.6

10.5

8-11

years

14.1

13.6

13.2

13.5

13.0

26.1

17.5

13.4

12.3

11.8

13.6

12.8

26.7

17.3

13.1

17.9

11.4

10.1

9.0

31.4

13.0

12

years

11.7

11.1

11.2

11.6

10.5

24.6

14.2

11.6

10.0

12.2

11.7

10.1

30.1

12.8

13.1

9.7

11.9

74.7

11.2

30.8

16.7

13-15

years

11.1

10.7

10.4

11.2

9.6

29.8

13.9

11.0

11.2

10.2

9.3

13.7

32.4

13.5

11.0

14.6

9.3

7.1

14.3

●8.3

●17.6

16 years

or more

9.3

8.7

10.3

8.6

11.6

32.5

8.7

9.9

9.2

10:5

9.7

9.4

“33.3

13.7

9.8

6.9

8.7

23.1

10.0

Not

stated

15.8

15.3

15.0

16,7

11.7

35.6

14.9

15.7

12.6

15.4

11.6

18.0

34.0

17.9

20.5

.

12.9

23.9

●12.5

●61.5

23.3

29
Table 5. Percent of infants of low birth weight by race: l.lnited States, each region, geographic division, and State, 1976

Area

United States .................. ............ ..................... ..... ......... .... ...................................... ...... .....

Northeast ............................................................... ................... ..................................... ..........

New England ......................................... ............ ............................ .. ..............................................

Maine ............................. ....................... ...... ............ ................................................. ..........................

New Hampshire ............. .. ................ ........... ..................................................................... ...................

Vermont .......................... ............ ...................................... .................................................................

Massachusetts ............................. .............................. ..... ................................... ............................. .....

Rhode Island ..... ....... .............................. .................. .................................................................... ......

Connecticut ....... ............... ............ ...... .... ...... ...... ...............................................................................

Middle Atlantic ............................................... ............ .............. ....................................................

New York ........ .................. .................................... ........................ .....................................................

New Jersey ....... .............. ............................ ........................................................................................

Penr&ylvania ................. .......................... .................. .......... ................................................................

North Central ..... ....................... .................................... ............. .............................................

East North Central ...................... ......................................... ............ ............. ................................

Ohio ..................................... ............................................................................ ..................... .............

Indiana ......................................... ......... ........................ .. .... ................................ ........... ....................

Illinois ......... ..... ........................................................ ...................... ..................... ...............................

Michigan ........... .................... .............................. ........................ ........................................................

Wisconsin ........... ................... ...................... .................... ................. .............. ........... ................... ......

West North Central .................................................... .......... .. ............ .................................... .......

Minnesota ................... .......................................... ...... ...... .... ...... .................... ............ ........................

lowa .............. ............................................................. ......................................... ...............................

Missouri .................................. ...... ....... ............................. ..... ...... .................... ........... ........................

North Dakota ........................................... ........................ ..................................................................

South Dakota ............. ............................. ...... .. ............ ....... .. ...... ..................... ...................................

Nebraska .......................... ...... .............................. ...................... .. .......................... ............................

Kansas ............................................ ........................................ ........................... .................................

South ................................... .................................................... ............. ........ ...........................

South Atlantic ................ ................ .............. .. ............ ............ ................................ ......................

Delaware ...................... .................. ..... .................. ...................................................... .......................

Ma~land ............................................................... ...... ................ .. .. .. .......................... .. .....................

Oistrict of Columbia ...... ........................................ ............ .......... .. ....... ........... ........ ...........................

Virginia ........... ........................ ............ .................. ...... ........ ............................ ............ ............. ..........

West Virginia. ................. ................................ .................... ...................................................... ..........

North Carolina ............ ........ ........................ .......... .......... ...... .. .... .. .............. ............ .... .. .....................

South Carolina ............... ...................... .......................... ...................... ..............................................

Georgia ............ ............................................ ............ .......... .. ............................ ...................................

Florida ...... ............................... ...... ....... ..... .................................. ............................ .......... ...............

East South Central ........... ...................... ........................ ...............................................................

Kantucky ......... ....... .................................... ........................ ...............................................................

Tennessee ..................... .. .... ........ ............ ............ ............ .......... .................... ..... .................................

Alabama .............................. ............. ........... ........................ ...............................................................

Mississippi ........ ........ ................................................................................... .... ................................ ...

Al I

races

7.3

7.5

6.5

5.8

6.4

6.1

6.4

6.6

7.2

7.8

8.2

7.5

7.3

6.8

7.1

6.9

6.6

7.6

7.4

5.8

6.2

5.5

5.9

7.3

5.1

5.3

6.0

6.4

8.0

8.2

7.8

8.1

12.0

7.5

7.0

8.3

8.9

8.7

7.8

8.0

7.3

7.8

8.2

9.0

~

White

6.1

6.4

6.1

5.8

6.4

6.1

6.0

6.3

6.3

6.5

6.8

6.2

6.2

5.8

5.9

5.9

6.0

5.9

6.1

5.4

5.7

5.3

5.8

6.2

4.9

5.0

5.7

5.9

6.4

6.2

6.2

6.0

6.9

6.0

6.9

6.3

6.2

6.4

6.1

6.5

6.7

6.4

6.3

6.3

Black

13.0

13.5

11.9

3.3

6.9

10.3

10.9

11.5

13,2

13.7

13.7

13.3

14.1

13.5

13.6

13.5

12.0

13.8

14.0

12.7

13.0

12.7

10.9

13.3

14.5

16.9

12.6

12.9

12.8

12.9

13.0

13.5

13.0

12.5

10.2

12.8

13.1

12.9

12.6

12.3

12.7

13.0

11.7

12.2

Other

races

&9

7.CI

7.C)

7.g)

43

7.7

6.6

5.7

8.7

7.C) ,

7.C)

6.CI

7.$)

6.3 .

6.CI

6.8

7.g)

5.8

5.41

5.7

6.13

7.31

7.CI

7.41

6.5

6.7’

54~

4Jj

6.9

7.2!

.

13.01

6.6

6.2!

6.5

7.8 .

8.7

5.4

4.8

7.7

8.zI

7.7’

9.a

9.8

6.4

30
Table 5. Percent of infants of low birth weight by race: United States, each region, geographic division, and State, 1976–Con.

4

Area

West South Central ........ ................. ...... .................................... ..... ............ ...................................

Arkansas .............................................. .............. ................. ...... ............................. ...... .......................

Louisiana ................... ........... ..... .......... ............ .. ........ .............. ............ .................. .............................

Oklahoma ............ ...... .................. ......... ........... .............. .................. ...... .............................................

Texas ............................. ................................. ..... ...... ................ ...... ...................................................

West ................ .. ..... ..... ................. ..... ..... ..... .... ....... .... ..... .................. .. ....................................4

Mountain ............................ ...... ................. .................... ................ ............ .................... ...............

Montana ... ......... .......... ...................... ...... .............. ...... ...... ..... ............................................................

ldaho .............................................................. ........ ........... .................................................................

Wyoming .................................... .......... .......... .......................... .............................................. ............

Colorado .................. .................. .... ...... .......... .......... .......... ........................ .............. ..........................

New Mexico ................... ............. ..... .......... ..... ..... .... .......... ...... ...................................... ....................

Arizona ..................... ........... ...... ............ .... .......... ................................ ............ .................... ..............

Utah ....................................... .................... .... .. .... ........... ............... ........ ............................................

Nevada .................................................... .... .... ...................... ...................... ....... .. ..............................

Pacific ........ ....................................... ...... .... .... ............ .......... .................... ............ .......... ..............

Washington ............... ............ ......................... ............... .................... ............. ............................. ........

Oregon .............. ........ .... ........................ .... ..... ..................... ...............................................................

California ......................... ......... ...................... .... ...............................................................................

Alaska .................................. ...... .......... .......... .................... ........... ....... .... ..........................................

Hawaii ......................................... ..... .... .......... .... ................ ................... ............................. ................

All White

races

7.8

7.9

9.0

7.5

7.5

6.4

7.1

6.7

5.8

8.8

8.8

8.1

6.3

5.4

7.7

6.1

5.5

5.4

6.2

5.3

7.7

6.5

6.5

6.3

7.0

6.5

5.9

6.9

6.4

5.8

8.5

8.5

8.2

6.1

5.4

7.0

5.5

5.2

5.2

5.5

5.0

6.6

Blaci

13.:

12.:

13.1

13.E

13.C

11.:

13.C

12.7

1.7

17.2

13.9

12.6

11.5

9.8

14.6

11.1

9.1

12.7

11.2

9.1

8.3

Other

races

6.4

5.4

6.4

5.9

7.6

7.0

7.3

9.2

6.7

13.9

10.3

7.3

6.0

7.1

5.5

6.9

6.9

6.2

6.5

5.6

8.1

.

31
APPENDIXES

I.

IL

111.

I.

CONTENTS

Technical Notes ................................ ...... .................................................... ....................................

Sources of Data ..................... ...... ......................................................... .....................................

Reporting Areas ............................................. ...................................... ............................ ..... ....

Sampling Rates ................. ......................... .......................................................... ............ ........e

Residence Classification ....................... .....................................................................................

Completeness of Reporting and Reporting Bias ............................ ... ................................... ......

Definition of Terms ............................... ..... ...... ............................... ...............................................

Direct Standardization of Percent Low Birth Weight by Maritaf Status and Month of Pregnancy

Prenatal Care Began ............ ......................... ........... .......................... ..............................................

APPENDIX TABLE

States reporting educational attainment of mother, dates of last live birth and fetal death, date

last normal menstrual period began, month of pregnancy prenatal care began, and marital status

of mother: United States, 1976 .............. ..................................... ................... ................................

33

33

33

33

33

33

36

37

34

.

.

32
APPENDIX I

TECHNICAL NOTES

Sources of Data

4

The data presented in this report are derived

from birth certificates filed in each of the

registration areas of the United States. Additional data are published annually by the Na-

.

tional Center for Health Statistics in Volume I

of Vital Statistics of the United States and are

also available in the form of unpublished tabulations. A complete discussion of the sources,

classification, and processing of natality data

may be found in the technical appendixes of

these volumes.

Repotting Areas

The birth certificates of all reporting areas

include a question on weight at birth. However,

not all areas request information ,on other

characteristics discussed in this report. Table I

shows the areas that request educational attainment of mother, dates of last live birth and fetal

death (used to derive statistics on outcome of

. last pregnancy and interval since termination of

last pregnancy), date last normal menstrual

period began (for deriving period-of-gestation

data), month of pregnancy prenatal care began,

& and marital status of mother. The size of the

reporting area is, therefore, dependent on

which characteristics are included in a particular

analysis.

Sampling Rates

Data for 1950 and 1955 are based on the

total file. of birth records. Data for 1951-54,

1956-66, and 1968-71 are derived from 50-percent samples of birth records; data for 1967 are

based in part on 20-percent and in part on

50-percent samples. Birth statistics for the years

1972-76 are based on 100 percent of the birth

certificates from States p-anticipating in the

Cooperative Health Statistics System (CHSS)

and a 50-percent sarnpIe of births from all other

States. Beginning in 1972, States providing data

through CHSS were Florida, Maine, Missouri,

New Hampshire, Rhode Island, and Vermont.

The following States were added in subsequent

years: Colorado, Michigan, and New York (excluding New York City) in 1973; Illinois, Iowa,

Kansas, Montana, Nebraska, Oregon, and South

Carolina in 1974; Louisiana, Maryland, North

Carolina, Oklahoma, Tennessee, Virginia, and

Wisconsin in 1975; and Alabama, Kentucky,

Minnesota, Nevada, Texas, and West Virginia in

1976. A discussion of sampling procedures and

sampling errors can be found in the technical

appendix of Volume I of Vital Statistics of the

Unz’tedStates for these years.

Residence Classification

All tables included in this report are by place

of residence. Births to U.S. residents occurring

outside this country are not included. All tables

showing time series include data for Alaska

beginning in 1959 and for Hawaii beginning in

1960.

Completeness of Reporting

and Reporting Bias

There has been nearly complete reporting of

weight at birth on birth certificates since 1959.

During the period 1959-76, information was

missing from less than 1 percent of all birth

certificates.

For the years 1950-55, the birth certificates

of Connecticut and Massachusetts did not in33
Table i. States reporting educational attainment of mother, dates of last live birth and fetal death, date last normal menstrual period

began, month of pregnancy prenatal care bagan, and marital status of mother: United States, 1976

[ Items shown are those on the Standard Certificate of Live Birth. X denotes presence of item on the State certificate]

State

Alabama . ............... .................................................... ......................

Alaska .............. ...................................................... ............. ....... .....

Arizona ........................ ..... ......... ............ .........................................

Arkansas .......................................... .................................... ...... .....

California ..................... ......... ..........................................................

Colorado .. ................. .......... ............... .... .................. ...... ...... ...... .....

Connecticut ......................... ........................... ........... .....................

Delaware ................. .................... ........................ .. ..........................

District of Columbia . ............................. ...................... ......... .. ........

FJorida .............. ..............................................................................

Georgia ........................... .. ................... ....................... ..... ...............

Hawaii ........................ ........................... .......... ... .... ............. ............

Idaho .................... ...... ............................... ............................... ......

Illinois .................... .... .............. ...... ................... ........... ...................

Indiana ........... ...... ........ .................................................. .................

lowa ... ................................................... ............. ....... ............ ..........

Kansas ................... ............................ ....................... .......................

Kentucky ......... ......... ...... .................. ...... ........ ...... ..... ................. ....

Louisiana ... ............... ................................................. .....................

Maine ... ................... .. ............ .............. ............................................

MaWland ........... .. .......... .............. ....................................................

Masmchuwtts ......................................................... .........................

Michigan ...... ................... .............. ............ ......................................

Minnesota ............ .................. .........................................................

Mississippi ........... ....................................... ..... .. ..............................

Missouri ............................. ........ ...... ................ ....................... ........

Montana ........ ......... ........... ...................................... .. .. .. ...... ............

Nebraska ........................... .......... ......... ....... ....................................

Nmada ............................................. ........... .................... ...... .... ......

New Hampshire .......... ....... .................... .................... ..... .................

New Jersey ................................ .............. .... ........ ............ ................

New Mexico .................. .......................... ....... ........................... .. ....

New York ....... ...................................... ................................ ..........

. North Carol ina ....... ............................................ .............................

North Dakota ........................ .............................................. ........ ....

Ohio .. ............................ .................... .. ............................. .. .............

Oklahoma ....... ............................ ................... ........................ .........

Oregon ...................... .................... ..... ....... ................ ......................

Pennsylvania ............. ................................... ............................... ...!

Rhode Island .............................................. .... ...... ..........................!

South Carolina ......... .. ...................................... ...... ...... ................ ..

South Dakota ............ ............ .................... .................................. ...,

Tenneswe .......... .............................................. .................. ..............

Texas .................................................. .................. ............ .............

Utah .......................... ...... ...................................... ................. ........

Vermont ......................................................... .... .... .......................

Virginia ....................................................................... .................. .

Wash ington ...................... ................................ ..............................

West Virginia ..................... ............. .. ..... ........... ........ .............. .. ......

Wisconsin. ................................................................. .....................

Wyoming ............. .. .........................................................................

durational

Attainment

x

x

x

x

x

x

x

x

x

x

x

x

x

x

‘x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

Date of

last live

birth and

fetal daath

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

Date last

normal manstrual period

bagan

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

Month of

pregnancy

prenatal

care bagan

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

Maritall

status

of

mother

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

.

34
elude a question on birth weight. In 1956 the

information became available for Connecticut

for part of the year, and for the years 1957-58

only Massachusetts failed to include this item on

its live ‘birth certificates. Beginning with 1959,

birth weight was included on the birth certificates of all States. The birth certificate of New

Jersey did not include a question on race for the

years 1962 and 1963.

A “followback” survey covering births to

married women in 197238 permitted comparison of the reporting of birth weight on” birth

certificates with information reported on hospital records. There was perfect agreement in

reported birth weight for 87 percent of the

comparison cases and agreement in classifying a

birth as either low birth weight or heavier weight

in 96 percent of the cases.

NOTE: A list of references follows the text.

.

4-

35
APPENDIX II

DEFINITION OF TERMS

Birth weight. –In almost all areas, birth

weight is reported in terms of pounds and

ounces rather than grams. However, the metric

system has been used in tabulating and presenting the statistics to facilitate comparison with

data published by other groups. The equivalents

of the gram intervals in pounds and ounces are

as follows:

500 grams or less = 1 lb 1 oz or less

501-1,000 grams =llb20z-21b30z

1,000-1,500 grams =21b40z-31b40z

1,501-2,000 gHU_IIS =31b50z-41b60z

2,001-2,500 grams =41b70z-51b80z

2,501-3,000 grams =51b90z-61b90z

3,001-3,500 grams =61b100z-71blloz

3,501-4,000 grams = 7 lb 1202-8 lb 1302

4,001-4,500 grams = 8 lb 1402-9 lb 1402

4,501 grams or more = 9 lb 15 oz or more

For purposes of classification, infants weighing

2,500 grams or less at birth are considered to be

of low birth weight. Infants for whom birth

weight was not reported are excluded from the

computation of percents and medians.

Period of gestation.–The period of gestation is defined as beginning with the first day of

the last normal menstrual period (LMP) and ending with the day of birth. The LMP is used as

the initial date since it can be more accurately

determined than the date of conception, which

usually occurs about 2 weeks after the LMP.

Births occurring prior to 37 weeks of gestation

are considered to be preterm or premature for

purposes of classification. This distinction is in

accordance with that ado”pted by the World

Health Organization Expert Group on Prematurity established in 1950. *

Race and on”pn. –Births are classified

according to the race or origin of the parents.

The categories are “white,” “black,” “Ameri.

can Indian,” “Chinese,” “Japanese,” “Hawai- .

ian,” “Filipino,” and “other.” The category

“white” comprises births reported as white,

Mexican, Puerto Rican, Cuban, and, prior to

1964, all births for which race or origin was not

stated. The category “all other” Compfises

black, American Indian, Chinese, Japanese,

Hawaiian and part-Hawaiian, Filipino, and

“other.” The “American Indian” category includes Alaskan and Canadian Indians, Eskimos,

and Aleuts. Since the race of the mother and

child are identic~ for most births, for ease and

clarity in writing this report, the racial identification given to the mother is that of the child.

Outcome of and internal since last pregnancy. –Data on the outcome of and the interval

since the termination of the last pregnancy are

derived from the date of birth, date of last live .

birth, and date of last fetal death. Multiple

births are excluded from the computation of

these measures.

Urban places. –Urban places are classified 4

according to the population enumerated in th{:

1970 Census of Population. They include incorporated cities of 10,000 population or more,

and towns in New England, townships in New

Jersey and Pennsylvania, and counties in other

States that meet certain criteria. The remaining

nonurban areas of the country and smaller urban

places of less than 10,000 population are included in the category “balance of area.”

36
APPENDIX III

DIRECT STANDARDIZATION OF PERCENT LOW BIRTH WEIGHT BY MARITAL

STATUS AND MONTH OF PREGNANCY PRENATAL CARE BEGAN

To compare the percent low birth weight of

infants born to married and unmarried mothers

without the influence of differences in educational attainment and age composition, the

direct method of standardization was used. The

standard population was the distribution of all

births in 1976, regardless of marital status, by

educational attainment and age of mother.

Standardization was performed separately for

each racial group using the following formula:

z me =Pe,a #

e,a

ml = x 100

P

where

ml = standardized percent for given race,

m ,,= = percent low birth weight for each education, age group for given race,

Pe,a

= number of births in 1976 for each

education, age group for given race,

P = total standard population for given

race.

Simihirly, the percent low birth weight by

month prenatal care began was standardized

within each age group for differences in mother’s educational attainment. For each age group,

the standard population was the distribution of

births for that age by the educational attainment

of the mother. Standardization was done separately for each race. The percent of all other infants of low birth weight born in 1968 was

standardized to ekninate the effect of changes

in the proportions of infants delivered in and

out of hospitals since 1950. The standard population used was the distribution of infants delivered in and out of hospit& in 1950.

000

37

*U.S.GOVERNMENT PRINTING OFf ICE:19S7- 191-332:60375
VITAL AND HEALTH STATISTICS Series

Series 1. Programs and collection ProccdurcX. -. Reports which describe the genera] programs of the National

center for Health Statistics and its offices and divisions and data collection methods used and include

definitions and other materiaI neccssm-y for understanding the data.

Series 2. Data Evaluation and ,Wethods Research. –Studies of new statistical methodology including experimental tests of new survey methods, studies of vital statistics collection methods, new analytical

techniques, objective evaluations of reliability of collected data, and contributions to statistical theory.

Series 3. Analytical Studies. –Reports presenting analytical or interpretive studies based on vital and heaIth

statistics, carrying the analysis further than the expository types of reports in the other series.

Series 4. Documents and Committee Reports. - Final reports of major committees conccrncd with vital and

health statistics and documents such as recommended model vital registration laws and revised birth

and death certificates.

Series 10. Data From the Health Interview Survey. –Statistics on illness, accidental injuries, disability, usc of

hospital, medical, dental, and other services, and other health-related topics, all based on data collected

in a continuing national household interview suwey.

Strim 11. Data From the Ilealth Examination Survey and the Health and Nutrition Examination Survey. –Data

from direct examination, testing, and measurement of national samples of the civilian noninstitutionalized population provide the basis for two types of reports: (1) estimates of the mcdicaI1y defined

prevalence of specific diseases in the United States and the distributions of the population with respect

to physical, physiological, and psychological characteristics and (2) analysis of relationships among the

various measurements without reference to an explicit finite universe of persons.

Sers”es12. Data From the Institutionalized Population Surveys. -Discontinued effective 1975. Future reports from

these surveys will be in Series 13.

Series 13. Data on Health Resources Utilization. –Statistics on the utilization of heaIth manpower and facilities

providing long-term care, ambulatory care, hospitaf care, and family planning services.

Series 14. Data on Health Resources: Manpower and Facilities. –Statistics on the numbers, geographic distribution, and characteristics of health resources including physicians, dentists, nurses, other health

occupations, hospitals, nursing homes, and outpatient facilities.

Series 20. Data on Mortality. –Various statistics on mortality other than as included in regular annual or monthly

reports. Special analyses by cause of death, age, and other demographic variables; geographic and timc

series analyses; and statistics on characteristics of deaths not available from the vital records based on

sample sumeys of those records.

Series 21. Data on Nata/ity, Mamiage, and Divorce. –Various statistics on natality, marriage, and divorce other

than as included in regular annual or monthly reports. Special analyses by demographic variables:

geographic and time series amdyscs: studies of fertility; and statistics on characteristics of births not

available from the vital records based on sample surveys of those records.

Series 22. Data From the National Mortaiity and Nataiity. Surveys. -Discontinued effective 1975. Future reports

from these sample susveys based on vital records will be included in ScriCS 20 arid 21, respectively.

Sm.es 23. Data From the National Survey of Family Growth. –Statistics on fertility, famity formation and dissolution, fantiIy planning, and related maternal and infant health topics derived from a hicnnial survey

of a nationwide probability sample of ever-married women 15-44 years of age.

For a list of titles of reports published in these series, write to: Scientific and Trchnical information Branch

Nation*l Center for IIcalt}i Statistics

Public Ifcalth Scrvicc

Iiyaitstilk, Md. 20782
●

NCHS

U S DEPARTMENT Of IIEAL7H. EDUCATION, AND Wf LfAflE

%OIIC Hralth %wrr

Offe.1 Hrallh Reiesch. Stamtm. ●d Trchmwv

NMwmal Gntm k), Heatlh Sta,,,tw,

37CKIfti Wr’a Mlahwa”

Hv.t!$vdlC Mw4wnl 20?8? TMl~O CLASS

Of FICIAL BuSINESS

P! NALTY FOR PRIVATE uS(, S302

POSTAGE ANO FEES PAtO

(2

* u.S OEPAfl TMENT OF H.E W. _

uS.MML

HEW 396

P==l 1, ).J . ..1 //, ,,/)h .,.,,,,,, .