Vital and 

Health Statistics 

Trends in Low 

Birth Weight: 

United States, 1975-85 

Series 21: 

Data on Natality, Marriage, and Divorce 

No, 48 

National and regional trends in rates of low, moderately low, and very low 

birth weight are analyzed for the period 1975-85. Also reviewed are 1985 rates 

of low, moderately low, and very low birth weight in relation to a number of 

maternal and infant characteristics, as well as changes in low birth weight 

rates between 1980 and 1985 for many of these characteristics. 

US. DEPARTMENT OF HEALTH AND HUMAN SERVICES


Public Health Service


Centers for Disease Control


National Center for Health Statistics


Hyattsville, Maryland


October 1989


DHHS Publication No. (PHS) 89–1926

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Copyright information 

All material appearing in this report is in the public domain and may be 

reproduced or copied without permission; citation as to source, however, is 

appreciated. 

Suggested citation 

Taffel SM. Trends in low birth weight: United States, 1975-65. National Center 

for Health Statistics. Vital Health Stat 21(48). 1989. 

library of Cmgfeas Cetatoging-in-Pubkstion Date 

Trends in low birth weight: United States, 1976+5. 

p. cm.-(Vital and health statistics. Series 21, Data from the national vital 

statistics system : no. 48) (DHHS publication ; no. (PHS) 89-1926) 

Includes bibliographical references. 

Supt. of Dots. no.: HE20.6209:21/48 

ISBN &6406-041 9-X 

1. Birth weight, Low—United States—Statistics., 2. Birth weight, Low-Social 

aspects-Statistice. 3. Childbirth-United States—Skfistice. 4. United StateeStatistical, Vial. L National Center #H~lth Statistics (U.S.) Il. Series. 

Ill. Series: DHHS publication ; no. (PHS) 

HA21 1.A3 no. 46 F .1yg26” 

[RJ60] 

304.63097302t e-dc2# -o m 

[614.5992] 89-600242 

CIP 
,,{’ 

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I 

National Center for Health Statistics 

Manning Feinleib, M. D., Dr. P. H., Director 

Robert A. Israel, Deputy Director 

Jacob J. Feldman, Ph. D., Associate Director for Analysis 

and Epidemiology 

Gail F. Fisher, Ph. D., Associate Director for Planning and 

Extramural Programs 

Peter L. Hurley, Associate Director for Vital and Health 

Statistics Systems 

Stephen E. Nieberding, Associate Director for Management 

Charles J. Rothwell, Associate Director for Data Processing 

and Services 

Monroe G. Sirken, Ph. D., Associate Director for Research 

and Methodology 

Division of VW Statistics 

John E. Patterson, Director 

James A. Weed, Ph. D., Deputy Director 

Robert L. Heuser, M-A., Chiej Natality, Marriage and 

Divorce Statistics Branch 

Joseph D. Farrell, Chief, Systems and Programming Branch 

Mabel G. Smith, Chief Statistical Resources Branch 
Acknowledgment 

The helpful suggestions and assistance of Dr. Joel C. 

Kleinman of the National Center for Health Statistics in the 

review of this report are gratefully acknowledged. 

. 

Ill 

.-. . 
Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...””” 111 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Background, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . 1 

Highlights. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Changesinlowbirthweight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Nationaltrends . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . 3 

Regionaltrends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,. . . . . . . . . . . . . 3 

Matemalandinfantcharacteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Periodofgestation . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Ageofmotherandiive-birthorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Educational attainmentofmother . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

Interval sincelastlivebirth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Marital statusofmother . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 

Prenatalcare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

Listofdetailedtables . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 

Appendixes 

I. Sourceofdataandsamplingrates . . . . . . . . . . . . . . . . . . . . . . . . . 27 

II. Definitionsofterms . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . 28 

IH. Completenessofreporting . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . 29 

IV. Standardizationforeducational attainment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 

Listoftexttables 

A. Number of live births and percent distribution by birth weight, according to race of child: United States, selected 

years, 1975–87 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

B. Rates of low birth weight and very low birth weight, by mother’s region of residence and race of child: 

UnitedStates, 1975,1980,1985 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

C. Percent distribution of low-, moderately-low-, and very-low-birth-weight births by period of gestation, according to 

race of child: Total of 49 reporting States and the District of Columbia, 1981, and United States, 1985 . . . . . . . 7 

D. Rates of full-term and preterm low birth weight, by race of child: Total of 49 reporting States and the District of 

Columbia, 1981, andUnitedStates, 1985 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

E. Rates of low, moderately 10W, and very low birth weight, by age of mother and race of child: 

UnitedStates,1985 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

F. Rates of low, moderately low, and very low birth weight, by educational attainment of mother and race of child: 

Total of47reporting Statesandthe DistrictofColumbia, 1985 . . . . . . . . . . . . . . . . . . . . . 12 

G. Rates of low, moderately low,and very low birth weight, by interval since last live birth and race of child: Totalof 

49reporting StatesandtheDistrictofColumbia, 1985 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 

H.	 Rates of low, moderately low, and very low birth weight for full-term births, by interval since last live birth and 

race of child: Total of49 reporting States and the District of Columbia, 1985 . . . . . . . . . . . . . . . . . . . 13 

v 
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— 

J. Rates of low, moderately low, and very low birth weight, by marital status of mother and race of child United, 

States, 1985 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

K. Rates of low, moderately low, and very low birth weight for full-term births, by month of pregnancy prenatal’ care 

began andrace ofchild: United States, 1985 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...”.. 

L.	 Rates of low birth weight for full-term births, by month of pregnancy prenatal care began and race of child: Total of 

49 reporting States and the District of Columbia, 1981, and United States, 1985 . . . . . . . . . . . . . . . . . . 

M.	 Observed and adjusted rates of low, moderately low, and very low birth weight for full-term births, by month of 

pregnancy prenatal care began and race of child: Total of 47 reporting States and the District of Columbia, 1985 . . 

List of text figures 

16 

17 

18 

18 

4 

6 

9 

11 

12 

14 

1,5 

17 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

I 

Rates of low, moderately low, and very low birth weight for white and black births: United States, selected years, 

1975–87 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 

Percent distribution of live births by birth weight for white and black births: United States, 1975, 1985, and 

1987 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Rates of low birth weight, by period of gestation, for white and black births: United States, 1985 . . . . . . . .:. . 

Rates of low and very low birth weight, by age of mother, for white and black births: United States, 1985 . . . .. . 

Rates of low birth weight, by educational attainment and age of mother: Total of 47 reporting States and the District 

of Columbia, 1985 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Rates of low birth weight for full-term white births, by interval since last live birth, age, and educational attainment 

ofmother: Total of reporting areas, 1985 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Rates of low birth weight for full-term black births, by interval since last live birth, age, and educational attainment 

ofmother: Total of reporting areas, 1985 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Rates of low birth weight for women aged 20 years and over, by educational attainment and marital status of 

mother and race of child: Total of 47 reporting States and the District of Columbia, 1985 . . . . . . . . . . . . . . 

. . . 

— 

0.0 

z 

* 

# 

Symbols 

Data not available


Category not applicable


Quantity zero


Quantity more than zero but less than


0.05 

Quantity more than zero but less than 

500 where numbers are rounded to 

thousands 

Figure does not meet standard of 

reliability or precision 

Figure suppressed to comply with 

confidentiality requirements 

vi 
Trends in Low Birth Weight: 

United States, 1975-85 

by Selma M. TaffeJ, Division of Vital Statistics 

,. 

r. 

Introduction 

Background 

The incidence of low biqh weight (less than 2,500 grams, 

or 5 ‘/2 pounds) has been carefully monitored in the United 

States, because’ it’ is one of the major “predictors of infmt 

morbidity and mortality. ~ singleton infants born in 1980, 

the risk of dying in the ‘first year of life was 94 times higher 

for babies weighing less than 1,500 grams (very low birth 

weight) tlian for “tho’seweighing at least 2,500 grams, and 

7 times higher for those weighing 1,500-2,499 grams (moderately low birth weight) than for those weighing more. Of 

white babies who died in the first year of life, 53 percent 

weighed less than 2,500 grams; the comparable proportion 

of black babies who died was 63 percent. The risk of dying 

at less than 1 year of age declines dramatically with increasing 

birth weight, regardless of gestational age, live-birth order, 

maternal age, maternal education, or month prenatal care 

began (l). 

A recent review of the studies of surviving low-birthweight infants indicates that such babies are three times as 

likely as those of normal weight to have neurodevelopmental 

handicaps, twice as likely to have a serious congenital anomaly, and more likely to develop lower respiratory tract conditions, and, in general, are at increased risk of having a serious 

or prolonged illness (2). 

The information presented in this report is derived fi-om 

entries on live-birth certificates. For 1985, rates for all low 

birth weight (LBW) and those for its two components, moderately low birth weight (MLBW) (1,500-2,499 grams, or 3 

pounds 4 ounces to 5 pounds 8 ounces) and very low birth 

weight (VLBW) (less than 1,500 grams, or 3 pounds 4 ounces), 

are examined in relation to a number of maternal and infant 

characteristics. Also reviewed are national and regional 

changes between 1975 and 1985 in the incidence of LBW 

and VLBW, as well as 1980-85 changes in LBW in relation 

to period of gestation; maternal age, marital status, and educational attainment and month of pregnancy prenatal care began. 

Special consideration is given to the relationship between 

period of gestation and birth weight. For ease in discussion, 

the terms “women” and “mothers” are sometimes used interchangeably for “births .“ 

While this report was in preparation, data for the years 

1986 and 1987 on low birth weight and its components became 

available. Information for these years is therefore included 

in trend tables and graphs to show more current trends. 

Highlights 

Between 1975 and 1985, the incidence of low birth weight 

in the United States declined by 9 percent, from 73.9 to 

67.5 low-birth-weight babies per 1,000 live births, but 86 

percent of this decline occurred between 1975 and 1980. 

Although LBW declined for both white and black births between 1975 and 1980, the decline was nearly twice as great 

for white (9 percent) as for black births (5 percent). The 

decline in LBW rates in the 1980-85 period was 1 percent 

or less for both white and black births. Between 1985 and 

1987, LBW rates increased by slightly less than 1 percent 

for white births and by 2 percent for black births. 

Moderately low birth weight declined by 9 percent between 1975 and 1980 and by an additional 3 percent between 

1980 and 1985. In both periods, MLBW declined for both 

white and black births. From 1985 to 1987, MLBW rose 

by 1 percent for white births and by 2 percent for black 

births. 

The incidence of very low birth weight remained almost 

unchanged between 1975 and 1980 (11.6 very-low-birthweight babies per 1,000 live births in 1975, compared with 

11.5 in 1980) but increased by 5 percent (from 11.5 to 12.1) 

from 1980 to 1985. The increase in VLBW was about twice 

as great for black as for white babies (9 percent, compared 

with 4 percent). The increase in VLBW for this latter period 

reflects a rise in the VLBW rate for premature births as 

well as a shift to shorter gestational periods for VLBW babies. 

There was no change in the incidence of VLBW for white 

births from 1985 to 1987, but it rose 3 percent for black 

births. 

There were declines in LBW rates in all regions in the 

1975–85 period, but the declines were greatest in the Northeast. 

Rates of VLBW declined only in the Northeast and Midwest 

regions between 1975 and 1980 and rose in all regions between 

1980 and 1985. For both LBW and VLBW, changes were 

more favorable in the 1975–85 decade for white than for 

black births in all regions, thus increasing the racial differential 

in each region. 

1’

For all characteristics examined, rates of low birth weight, 

moderately low birth weight, and very low birth weight are 

substantially higher for black than for white births. The racial 

differential is most pronounced for very low birth weight. 

In 1985, the VLBW rate was 2.8 times as high for black 

as for white babies, and rates of LBW and MLBW were 

2. 1–2,2 times as high for black as for white births. 

More than half of all LBW and MLBW babies and more 

than 9 in 10 VLBW babies are born before 37 weeks of 

gestation (preterm). Of LBW babies who were full term, 

only 3 percent weighed less than 1,500 grams, but of those 

born preterm, 27 percent weighed this little. For both preterrn 

and full-term LBW babies, the proportion weighing less than 

1,500 grams is higher for black than for white babies. 

As the gestational period lengthens, the incidence of low 

birth weight declines rapidly. The risk of LBW and MLBW 

is higher for white than for black babies before 36 weeks 

of gestation but is higher for black babies at longer gestational 

periods; the risk of very low birth weight is higher for white 

babies only up to 32 weeks of gestation. One of the main 

reasons that LBW, MLBW, and VLBW rates are higher for 

black than for white births is that black babies are more 

likely to have a short gestation. 

Between 1981 and 1985, the rate of full-term LBW declined by 7 percent, but the rate of preterm LBW increased 

by 2 percent. Thus the small decline in the overall rate of 

LBW in the 1981–85 period is due entirely to the reduction 

in the rate of full-term LBW. 

Rates of LBW, MLBW, and VLBW are lowest for mothers 

in their late twenties and rise as maternal age increases or 

decreases. Age differences are far more pronounced for white 

than for black mothers. All LBW rates are substantially higher 

for young women having a second or higher order birth than 

for first-time mothers, reflecting the close spacing of many 

second and subsequent births. 

In 1985, babies born 1–1YZvears after the previo~s live 

birth were two-thirds more likel~ to have a low birth weight 

and about 80 percent more likely to have a very low birth 

weight than babies born 24 years after the previous” live 

birth, This differential is less but is still substantial when 

the comparison is limited to fill-term births (at least 37 weeks 

of gestation). 

Between 1980 and 1985, the risk of low birth weight 

declined by 4 percent for mothers with 16 years or more 

of schooling but declined by only 1 percent or rose by up 

to 3 percent for women with less education. Women with 

at least 16 years of schooling are the least likely to bear 

an LBW, MLBW, or VLBW baby, but differences in outcome 

by educational attainment are distinctly less pronounced for 

black than for white mothers. 

The decline in the rate of low birth weight between 1980 

and 1985 was greater for unmarried than for married mothers 

(6 percent, compared with 4 percent), reflecting a shift to 

older ages of childbearing and higher levels of educational 

attainment for unmarried women. Regardless of marital status, 

the decline in rates is less for black than for white mothers. 

In 1985, unmarried black mothers were 1.6–1.9 times as’ 

likely to bear an LBW, MLBW, or VLBW baby as, were 

unmarried white mothers; the racial differential was even 

greater for married mothers. 

The relationship between month prenatal care began and 

risk of low birth weight can be. misleading unless worne’n 

who deliver prematurely are excluded from the comparison 1 

For full-term births (at least 37 weeks of gestation), the risk 

of LBW, MLBW, or VLBW is about twice as high for mothers 

starting care in the third trimester of pregnancy as for mothers 

beginning care in the first 2 months of pregnancy. However, 

adjustment for differences in mothers’ educational attainment 

reduces this differential. 
Changes in low birth weight ,!, .,— 

,. ., 

,.. ,. 

.’ 

.,. . 

,, . . 

National trends, 

Between 1975 and 1985, the rate of low birth weight 

declined in the United States, from”73.9 to 67.5 LBW babies 

per 1,000 live births. Most of this decline (86 percent) occurred 

“between’1975 and 1980. However, from 1985 to 1987, “the 

rate of LBW increased by 2 percent, to 69~0(table 1). ‘ 

There was a substantial reduction in low birth weigh~ for 

both white and ,black tiis “in the 1975-80 period, ‘but the 

rtiuction was nearly &vice as great for whhe btis (9 percent, 

comp%ed wik 5 percent), slightly increasing the racial differential in”rates. In 1975, the black rate (130.9) was 2.1 times 

as high as the whiti rate (62.6); in 1980, the LBW rate was 

124.9 for black births, 2.2 times the rate of 57.0 for white 

‘bfis. Between 1980 and 1985, low bti weight decliied by 

only 1 percent for ‘both white and black births. There was 

a reversal in ‘this downward trend for both races betsveen 1985 

“&id1987. The low birth weight rate increased by slightly less 

than 1 percent for white btis (to 56.8) and by 2 percent 

for black births (to 127.1) (tablel and figure 1). 

In recent yeaks growing aitention has been paid to the 

incidence of very low birth weight, because infants weighing 

this little are at greatest risk of dying or of having a serious 

illness. Infants weighing less than 1,500 grams comprise only 

about 1 percent of all live births, but they account for almost 

40 percent of all infant deaths (l). 

Between 1975 and 1980, the incidence of VLBW remained 

almost unchanged (11.6 per 1,000 live births in 1975 and 

11.5 in 1980), but between 1980 and 1985, the VLBW rate 

increased by 5 percent, to 12.1. Between 1985 and 1987, 

the VLBW rate again increased, to 12.4 (table 1). The VLBW 

rate for white births declined slightly between 1975 and 1980 

(from 9.2 to 9.0) but then rose to 9.4 in 1985 and remained 

at this level. in 1987. For black births, there was a rise in 

the VLBW rate during both periods, from 23.7 to 24.4 between 

1975 and 1980, with further increases to 26,5 by 1985 and 

27.3 by 1987 (table 1 and figure 1). 

The overall decline in low birth weight in the 1975–85 

period is thus attributable to the decline in the MLBW component. The rate of MLBW declined from 62.3 to 56.9 between 

1975 and 1980 and declined further to 55.4 by 1985. The 

overall decline in MLBW during the 1975–85 decade was 

somewhat higher for white (12 percent) than for black births 

(9 percent). 

Between 1985 and 1987, the MLBW rate rose by 1 percent 

for white births (to 47.4) and by 2 percent for black births 

(to 99.8). The overall increase in LBW rates in the 1985-87 

,, 

,,, 

., ,, , 

,, 

period reflects increases in both the moderate and very low 

birth weight components. 

Concomitant with the decline in low birth weight in the 

1975–85 decade, there was a reduction in the proportion of 

babies born weighing 2,50W3,499 grams and a distinct shift 

to birth weights of 3,500 grams (7 pounds 12 ounces) or 

more (table A and figure 2). By 1985, 41 percent of riewboms 

weighed at least 3,500 grams, up from 37 percent, in 1975. 

Because the increase in higher birth weights was of about 

the same magnitude for white as for black births, there, was 

no narrowing of the racial difference. In 1985, as in 1975, 

the -proportion of white newborns weighing at least 3,500 

grams was 1.7 times the comparable proportion of black newborns (44 percent, compared with 26 percent in 1985). Bi@ 

weight distributions changed very little between 1985 qid 

1987 for either racial group. ,,. 

Regional trends 

The rate of low birth weight in the United States declined 

by 7 percent (from 73.9 to 68.4) in the’ f975–80 period. 

The decline was of approximately the same magniiude in 

he Northeast (9 percent) as in the Midwest and ‘West 

(8 percent). The lowest decline was in the South (6 percent). 

During this period, declines in low birth weight were substantially higher for white than for black births in all regions, 

which resulted in a widening of the differential between black 

and white births in each region (table B). 

Between 1980 and 1985, there were much smaller declines 

in three regions and an increase in one region in the rate 

of low birth weight. The rate for the Northeast declined the 

most (4 percent), with considerably lower declines in the 

Midwest (1 percent) and the South (2 percent); low birth 

weight rose by 1percent in the West. 

Although the”incidence of very low birth weight declined 

by 1 percent (from 11.6 to 11.5) between 1975 and 1980 

in the United States as a whole, it rose by 4 percent in 

the West, remained unchanged in the South, and declined 

2–3 percent in the Northeast and Midwest regions. In all 

regions, changes in the 1975–80 period were more favorable 

for white than for black births (table B). 

Very low birth weight rates rose in all regions between 

1980 and 1985, with the greatest increase in the South 

(8 percent). The large increase in the South reflects substantial 

rises for both white (8 percent) and black (10 percent) births. 

Very low birth weight rose 2 percent in the Northeast, 

6 percent in the Midwest, and 4 percent in the West. 

3 
.@ 

140 

130.9 � 1975 

m 127.1 � 1980 

� ,,85 

120 

� 1987 

107.2 

100 

80 

62.6 

60 

53.4 

40 

26,5 27.3 

20 

0 

LOW birth Moderately low Very low LOW birth Moderately low Very low 

weiaht birth weight birth weight weight birth weight birth weight 

White births Black birihs 

NOTE Lowbirthweightis weightlessthan2,500 grams(5 pounds8 ounces); moderately low birlh weight is 1,500-2,499 grams (3 pounds 4 ounces to 5 pounds 8 ounces); very low birth weight is less than 1,500 grams (3 pounds 4 ounces). 

Figure 1. Rates of low, moderately low, and very low birth weight for whtie and black birtha: United States, selected years, 1975-S7 
Table A. Number of live births and percent distribution by birth weightj according to race of child Un~ed Stateaj seleoted yearaj 1975-87 

Birth weight 

All Less than 1,000- 1,500- 2,00C- 2,500- 3,00& 3,500- 4,00& 4,500 

Race of child All live birth 1,000 1,499 1,999 2,499 2,999 3,499 3,999 4,499 grams 

and year biiths weights grams grams grams grams grams grams grams grams or more 

All races’ Numberz Percent distribution 

1975 . . . . . . . . . . . . . . . . . . . . . . . . . 3,144,198 100.0 0.5 0.6 1.4 4.8 17.9 37.9 27.4 7.8 1.6 

1980 . . . . . . . . . . . . . . . . . . . . . . . . . 3,612,258 100.0 0.5 0.6 1.3 4.4 16.3 37.0 29.1 8.9 1.8 

1985 . . . . . . . . . . . . . . . . . . . . . . . . . 3,760,561 100.0 0.6 0.6 1.3 4.2 15.9 36.7 29.6 9.2 1.9 

1966 . . . . . . . . . . . . . . . . . . . . . . . . . 3,756,547 100.0 0.6 0.6 1.3 4.3 15.9 36.7 29.5 9.2 1.9 

1987 . . . . . . . . . . . . . . . . . . . . . . . . . 3,809,394 100.0 0.6 0.6 1.3 4.3 16.0 36.7 29.5 9.1 1.9 

White 

1975 . . . . . . . . . . . . . . . . . . . . . . . . . 2,551,996 100.0 0.4, 0.5 1.2 4.1 16.2 37.8 29.3 8.6 1.8 

1980 . . . . . . . . . . . . . . . . . . . . . . . . - 2,898,732 100.0 0.4 0.5 1.1 3.7 14.6 36.6 31.1 9.9 2.1 

1985 . . . . . . . . . . . . . . . . . . . . . . . . . 2,991,373 100.0 0.4 0.5 1.1 3.6 14.1 36.1 31.7 10.3 2.2 

1986 . . . . . . . . . . . . . . . . . . . . . . . . . 2,970,439 100.0 0.4 0.5 1.1 3.6 14.2 36.1 31.6 10.3 2.1 

1987 . . . . . . . . . . . . . . . . . . . . . . . . . 2,992,486 100.0 0.4 0.5 1.1 3.7 14.2 36.1 31.6 10.3 2.1 

Black 

1975 . . . . . . . . . . . . . . . . . . . . . . . . . 511,561 100.0 1.1 1.2 2.6 8.1 25.7 38.4 18.4 3.8 0.7 

1980 . . . . . . . . . . . . . . . . . . . . . . . . . 589,616 100.0 1.2 1.2 2.5 7.6 24.3 38.4 19.8 4.3 0.8 

1985 . . . . . . . . . . . . . . . . . . . . . . . . . 608,193 100.0 1.4 1.2 2.4 7.4 23.6 38.4 20.3 4.5 0.8 

1986 . . . . . . . . . . . . . . . . . . . . . . . . . 621,221 100.0 1.4 1.3 2.5 7.4 23.6 38.2 20.3 4.5 0.8 

1987 . . . . . . . . . . . . . . . . . . . . . . . . . 641,567 100.0 1.5 1.3 2.4 7.5 23.5 38.0 20.4 4.5 0.9 

qIncludes races other than whtie and black.


‘Includes births with unknown birth weight, which are excluded from the computation of the percent distribution.


Table B. Rstes of low birth weight and very low birth weightj by mother’s region of residence and race of child: United States, 1975, 1980, and 1985 

Low birth weight’ Very low birth wefghtz 

Mother’s region of residence and mce of child 1975 1980 1985 1975-80 1980-85 7975 1980 1985 1975-30 1980-65 

All races3 Rateper1,0001ive births Percent change Rate per 1,000 live births Percent change 

United States . . . . . . . . . . . . . . . . . . . . . 73.9 68.4 67.5 – 7.4 -1.3 11.6 11.5 12.1 -0.9 5.2 

Northeast . . . . . . . . . . . . . . . . . . . . . . . 75.3 68.8 66.1 – 8.6 -3.9 12.1 11.9 12.1 -1.7 1.7 

Midwest . . . . . . . . . . . . . . . . . . . . . . . . 69.1 63.9 63.4 – 7.5 – 0.8 11.3 11.0 11.6 – 2.7 5.5 

South . . . . . . . . . . . . . . . . . . . . . . . . 61.9 77.0 75.6 – 6.0 -1.8 12.8 12.8 13.8 7.8 

West . . . . . . . . . . . . . . . . . . . . . . . . . 65.1 59.9 60.7 -8.0 1.3 9.3 9.7 10.1 4.3 4.1 

White 

United States . . . . . . . . . . . . . . . . . . . . . 62.6 57.0 56.4 – 8.9 -1.1 9.2 9.0 9.4 – 2.2 4.4 

Northeast . . . . . . . . . . . . . . . . . . . . . . . 65.1 58.4 55.3 – 10.3 -5.3 9.9 9.6 9.3 -3.0 – 3.1 

Midwest . . . . . . . . . . . . . . . . . . . . . . . . 59.3 53.6 53.4 -9.3 – 0.7 9.1 8.7 9.2 – 4.4 5.7 

South . . . . . . . . . . . . . . . . . . . . . . . . . 65.5 60.6 59.9 –7.5 –1.2 9.4 9.1 9.8 – 3.2 7.7 

West . . . . . . . . . . . . . . . . . . . . . . . . . 60.5 55.0 55.7 -9.1 1.3 8.4 6.6 9.1 2.4 5.8 

Black 

United States . . . . . . . . . . . . . . . . . . . . . . 130.9 124.9 124.2 – 4.6 -0.6 23.7 24.4 26.5 3.0 8.6 

Northeast . . . . . . . . . . . . . . . . . . . . . . . 133.4 124.6 122.4 -6.6 –1.8 25.1 25.1 27.3 — 8.8 

Midwest . . . . . . . . . . . . . . . . . . . . . . . . 135.5 130.2 128.4 – 3.9 -1.4 25.9 26.1 27.8 0.8 6.5 

South . . . . . . . . . . . . . . . . . . . . . . . . . 129.9 124.8 124.4 -3.9 – 0.3 22.8 23.8 26.2 4.4 10.1 

West . . . . . . . . . . . . . . . . . . . . . . . . . 120.4 113.8 118.3 – 5.5 4.0 21.3 22.6 24.3 7.0 6.6 

‘Less than 2,500 grams (5 pounds 8 ounces). 

‘Less than 1,500 grama (3 pounds 4 ounces). 

%cludes races other than white and black. 

5 
.

.

O-J 

White � ���� 40 37.8 � ���� 

31.7 31.6 � 1987 

30 

20 

10.3 10.3 

10 

4.1 343 3.7 

c 0.4 0.4 0.4 0.5 0.5 0.5 1.2 1.1 1.1 

.— 0

3 

.-

.!4

D

> 

0 L -0 

E

al Black 

P 40 38.4 38.4 380 : 

30 

25.7 

20.3 20.4 

20 

10 8.1 7.4 7.5 

‘Less 1,000- l,50& ‘2,000- 2,500- 3,00W 3,500- 4,00c!- 4,500 

than 1,499 1,999,. 2,499 2;999 3,499 3,999 4,499 grams 1,000 grams grams grams ‘. grams grams grams grams or more grams . . 

Bkthweight ,’ 

. . ,. .. . . . ,.-.. ~gure2;" Percent distribution ofl~ve"Mtihs bytifih weight forwhtie and black tiRh~United Statea, 1975, ~9Q5, and19<S7 .. - ‘, .. ,- .- .. ., . . K .,. 
Maternal and infant 

characteristics 

Low birth weight, moderately low birth weight, and very 

low birth weight rates differ substantially according to period 

of gestation; age, educational attainment, and marital status 

of the mother; month prenatal care began; race of the child; 

live-birth ordeq and interval since last live birth. The following 

sections focus on such variations in rates for 1985. In addhion, 

important changes in LBW rates in recent years for several 

of these characteristics are dkcussed. Yem-to-year comparisons of the incidence of very low birth weight for many 

of these characteristics may not be valid because of the small 

annual number of such births, and therefore are not included. 

Period of gestation 

In recent years, increased attention has been focused on 

the gestational period of low-birth-weight babies. The low 

birth weight of infants born before 37 weeks of gestation 

(preterm) is due to insufficient time in utero for full growth, 

while the low birth weight of full-term newborns (at least 

37 weeks of gestation) is considered to be caused by intrauterine growth retardation. Low-birth-weight infants who are 

small for their gestational age, whether full-term or preterm, 

have a much higher rate of congenital malformations than 

do low-birth-weight infants whose weight is more consistent 

with their gestational age (2,3). Low-birth-weight infants with 

short gestations have a greatly increased risk of dying within 

the first year of life (l). 

Beginning in 1981, weeks of gestation have been imputed 

for birth records with incomplete information on date of last 

normal menstrual period (LMP), which is the basis for computing period of gestation (4). Before 1981, period of gestation 

was computed only when the day, month, and year of LMP 

were all reported. Because of this change, comparisons of 

birth weight rates by period of gestation are made for the 

period 1981–85, rather than 1980-85. In 1985, all States 

asked for the date of last normal menstrual period on the 

birth certificate, but in 1981, New Mexico did not. 

In 1985, more than half of all LBW babies (59 percent) 

were born before 37 weeks of gestation. Slightly more than 

half (52 percent) of babies of moderately low birth weight 

were preterm, and, as would be expected, nearly all 

(93 percent) of VLBW babies were born before term. There 

was practically no difference between black and white LBW, 

MLBW, or VLBW babies in the incidence of prematurity. 

Prematurity increased by 4-5 percent for both white and black 

LBW and MLBW babies and by 1 percent for VLBW white 

and black babies during the 1981–85 period (table C). 

Table C. Percent distribution of low-, moderately-low-, and very-low-birth-weight births by period of gestation, according to race of child Total of 49 

repom”ngStates and the District of Columbia, 1981, and United States 1985 

Low birth weight’ Moderately low birth weightz Vety low birth weight3 

Period of gestation and race of child 1981 1985 1981-85 1981 1985 1981-85 1981 1985 1981-85 

Percent Percent Percent 

All races4 Percent distribution change Percent distribution change Percent distribution change 

All gestations . . . . . . . . . . . .. . . . . . . . . . . . . . . . 100.0 100.0 ... 100.0 100.0 ... 100.0 100.0 ... 

Under 37weeks . . . . . . . . . . . . . . . . . . . . . . . . . 56.4 5&6 3.9 49.5 51.6 4.2 91.5 92.6 1.2 

37weeks And over . . . . . . . . . . . . . . . . . . . . . . . . 43.6 41.4 -5.0 50.5 48.4 -4.2 8.5 7.4 -12.9 

White 

All gestations . . . . . . . . . . . . . . . . . . . . . . . . . . . 100.0 100.0 ... 100.0 100.0 ... 100.0 100.0 ... 

Under 37weeks . . . . . . . . . .. . . . . . . . . . . . . . . . 55.9 58.1 3.9 49.4 51.6 4.5 91.7 92.6 1.0 

37weeks And over . . . . . . . . . . . . . . . . . . . . . . . . 44.1 41.9 – 5.0 50.6 48.4 – 4.3 8.3 7.4 – 10.8 

Black 

Allgestations. . . . . . . . . . .. . . . . . . . . . . . . . . . 100.0 100.0 ... 100.0 100.0 ... 100.0 100.0 ... 

Under 37weeks . . . . . . . . . . . . . . . . . . . . . . . . . 58.0 60.4 4.1 50.1 52.0 3.8 91.8 92.8 1.3 

37weeks And over . . . . . . . . . . . . . . . . . . . . . . . . 42.0 39.6 –’5.7 . 49.9 48.0 -3.8 8.4 7.2 -14.3 

1Les5 than2,500 grams (5 poundsS ounces).


21,50 C-2,499 grams (3 pounds 4 ounces to 5 pounds S ounces). .(


3Lezs than 1,500 grsms (3 pounds 4 otinws).


41ncludes races other than white and black.


NOTE For 1981, excludes data for New Mexico, which did not require reporting of date of W normal menstrual period. 

7 
In 1985,82 percent of all low-birth-weight babies weighed 

1,500-2,499 grams, and 18 percent weighed less than 1,500 

grams. Of LBW babies who were full term, only 3 percent 

weighed less than 1,500 grams, but of those born preterm, 

more than one-fourth (27 percent) weighed less than 1,500 

grams. Black LBW babies are more likely than white LBW 

babies of comparable gestational periods to weigh less than 

1,500 grams. 

The incidence of low birth weight declines rapidly as 

the gestational period lengthens. In 1985, the rate of low 

birth weight was 768.0 per 1,000 births for gestations of 

less than 28 weeks, compared with just 14.6 for gestations 

of 41 weeks. The rate of low birth weight increased (to 21.0) 

for gestations of 42 weeks and over (table 2). 

Overall rates of low birth weight are shown apportioned 

between full-term and preterm LBW in table D. The rate 

of full-term LBW declined by 7 percent between 1981 and 

1985 while the rate of preterm LBW increased by slightly 

more than 2 percent. These changes were similar for white 

and black births. Thus the overall decline in low birth weight 

in this period is wholly attributable to the decline in full-term 

low birth weight. Because of the concomitant decrease in 

full-term and increase in preterm LBW, the proportion of 

all LBW babies who were born preterm rose from 56 percent 

in 1981 to 59 percent in 1985, continuing the trend of an 

increase in the proportion of preterm low birth weight observed 

in the 1970’s (5). 

The risk of low birth weight is greater for white than 

for black births before 36 weeks of gestation but is higher 

for black births at longer periods (figure 3). However, the 

rate of low birth weight in 1985 was 7 percent higher for 

preterm black (418.0 per 1,000) than for preterm white births 

(389.0), reflecting the much greater risk of LBW for black 

babies beginning at 36 weeks’ gestation. Full-term black babies 

were 2.3 times as likely as full-term white babies to have 

a low birth weight (57.9 per 1,000, compared with 25.0) 

(table 2). 

Rates of moderately low birth weight are also generally 

higher for white than for black births before 36 weeks of 

gestation. However, for preterm births as a group (gestational 

ages up to 37 weeks), rates of MLBW were nearly identical 

for white and black births (290.6, compared with “2866),, 

but black babies who were full-term were 2.3 time’s as “likely” 

as white babies to weigh 1,500-2,499 grams (55.7, compared 

with 24.3) (table 2). 

The risk of very low birth weight is less for black than, 

for white babies before 32 weeks of gestation. For both fullterm and preterm births as a group, black babies are substan-. 

tially more likely to weigh less than 1,500 grams than are’ 

white babies. However, for both racial groups, the risk of 

very low birth weight for full-term deliveries is minimal—less 

than I per 1,000 white births and about 2 per 1,000 black 

births, 

The increase of 5 percent in the VLBW rate in the first; 

half of the 1980’s is due to the small increase in the proportion’ 

of preterm births as well as to the increase in the VLBW 

rate for preterm births. 

Between 1981 and 1985, the decline in rate,s of low’ 

birth weight for both black and white births was substantially 

greater for fill-term than for preterm deliveries [5–7 percent, 

compared with 1 percent or less) (table 2). Thus the small, 

overall decline in LBW rates for both black and white births 

in this period is due mainly to the decline in low birth weight 

for babies with longer gestational periods. 

Age of mother and live-birth order 

Rates of LBW, MLBW, and VLBW are lowest for mothers 

25–29 years of age and increase with increasing and decreasing” 

age (table E and figure 4). The 1985 LBW rate of 128.5, 

for the youngest mothers (under 15 years of age) was 2.2 

times as high as the rate for women 25–29 years old (59.2); 

the rate for women 40 years and older (83.7) was 1.4 times 

as high as that for women aged 25–29 years. These age 

differentials are similar for MLBSV, but VLBW rates tend 

to be relatively higher for very young mothers. J 

Additionally, differences by age of mother for LBW, 

MLBW, and VLBW rates are greater for white than for black 

mothers. For example, the LBW rate in 1985 for white mothers 

15–19 years of age was 1.5 times the rate for &ose aged 

25–29 years (76.4, compared with 50.2); for black mothers, 

of Columbia, 1981, and , “ 

United States, 1985 

All racesl White Black ~ . 

Low birth weight 1981 1985 1981-85 1981 1985 1981-85 1981 1985 198’1+?5 

Rate per 1,000 Percent Rate per 1,000 Percent Rate per 1,000. Percent 

live births change live births change !iva birfhs change 

Alllowbirfh weight23, . . . . . . . . . . . . . . . . . . . 66.4 65,5 –1.4 55.2 54.7 -0,9 122.4 120.6, –1.5”., 

Full-term low birth weight’ ..,,... . . . . . . . . . . . 29.0 27.1 – 6.6 24.3 22.9 -5.8 51.4 47.8 – 7.0 

Preterm low birth weight 5..,,., . . . . . . . . . . . . 37.5 38.4 2,4 30.9 31.6 2.9 71.0 72.8 ‘2.5 “ 

Table D. Rates of full-term and preterm low birth weight by race of Cw[d: Total of 49 repofiingstates andthe Distffct

., 

1Includes races other than white and black. . . . ~ 

‘Excludes births with unknown period of gastation. 

%@ss than 2,500 grams (5 pounds 8 ounces). 

4Less than 2,500 grama and gestation of 37 weeks and over, 

5Leaa than 2,500 grams and gestation of Iesa than 37 weeks. 

NOTE: For 19S1, excludes data for New Mexico, which did not require reporling of date of last normal menstrual period, 

8 
800 

— White 

—— — Black 

\ 

\ 

\ 

700 

\ 

\ 

\ 

\ 

600 \ 

\\ 

\ 

\\ 

\ 

\ 

500 \ 

\ 

\ 

\ 

\ 

\ 

400 \ 

\ 

\ 

\ 

300 -“ 

200 

100 

_. —— - /“ 

-.—— —.-

0 1 1 1 I 1 1 1 t n I 1 1 I I 1 1 1 1 ! 

Under 28 29 30 31 22 33 34 35 36 37 38 39 40 41 42 43 44 45 and 

28 over 

Weeks of gestation 

3TE Low birth weight is weight less than 2,500 grams (5 pounds 8 ounces). 

Fgure 3. Ratea of low birth weight by period of gestation, for whtie and black bhtkx United State% 1985 

the teenage rate (133 .4) was only 1.1 times as high as the 

rate for mothers aged 25–29 years (119.8) (table E and 

figure 4). 

Increased maternal educational attainment is associated 

with a lower risk of low birth weight, as is dkcussed in 

the next section. For mothers 20 years and older, the rate 

of low birth weight is far lower for those with 16 years 

of schooling or more than for those with less education (figure 

5). However, the reduction in risk with increased schooling 

is greater ‘for white than for black births for all age groups. 

Regardless of the mother’s age, at each level of schooling, 

black babies are consistently at higher risk of low birth weight 

(table 3). 

Low ‘birth weight declined between 1980 and 1985 for 

women under 25 years of age but generally rose for mothers 

aged 25 years and over. By far the largest decline (12 percent)” 

was for girls under 15 years of age (table 4). Declines for 

women aged 15–24 years were 3 percent or less, but rates 

for mothers 25–34 years of age increased by up to 3 percent. 

A similar pattern is evident for both white and black births, 

but both the declines and the increases in rates are much 

larger for black births. 

Witiln each age group, there are large differences in 

the incidence of low, moderately low, and very low birth 

weight by the birth order of the child. As indicated in 

table 5, LBW, MLBW, and VLBW rates are substantially 

higher for teenagers and women in their early twenties having 

a third or higher order birth than for women in these age 

9 
Table E. Rates of low, moderately low, and very low birth weighg by age of mother and”race of child United States, 1985 

Low biflh weightl Moderately low birth weightz Very low birth weights 

Age of mother All races4 White Black All races 4 White Black All races4 White Black 

Rate per 1,000 live births 

Alleges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67.5 56.4 124.2 55.4 47.0 97.6 12.1 9.4 26.5 

Under 15 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128.5 104.6 147.5 96.7 75.0 113.0 31.9 29.6 34.5 

15-19years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.7 76.4 133.4 75.2 62.8 106.2 17.5 13.6 27.2 

15–17years . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.2 83.7 136.5 81.7 67.6 109.6 20.5 16.1 26.9 

16–19 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87.4 72.6 129.7 71.6 60.4 103.8 15.8 12.4 25.9 

20–24years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69.0 57.5 120.3 56.9 46.1 95.3 12.1 9.3 25.0 

25-29years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59.2 50.2 119.6 48.8 42.1 93.3 10.4 8.0 26.5 

30-34years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60.5 52.1 123.6 49.5 43.3 95.4 11.0 8.8 28.5 

35-39years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69.0 60.3 126.8 56.3 49.7 98.7 12.7 10.6 28.1 

40yearsandover . . . . . . . . . . . . . . . . . . . . . . . . . . 63.7 73.9 136.5 69.0 61.5 110.3 14.7 12.4 26.3 

1Lessthan 2,500 grams (5 pounds 8 ounces),


21,500-2,499 grams (3 pounds 4 ounces to 5 pounds 8 ounces)


aLessthan 1,500 grams (3 pounds 4 ounces),


41ncludes races other than white and black. 

groups having their first child. By contrast, rates are higher 

for women in their thirties having their first baby than for 

those having asecond or higher order birth. Thelowestincidence ofLBW, MLBW, and VLBW is for women 25–29 

yearsoldhavingtheir secondchild. 

The very high rates of LBW associated with higher birth 

orders for younger mothers reflect to some extent the closer 

spacing of such births, Also, young mothers are more likely 

to be socially disadvantaged than are older mothers (6). The 

incidence of LBW, MLBW, and VLBW and the interval 

between births are discussed in a later section. 

The largest declines in low birth weight in the period 

1980-85 were for teenagers having a second or higher order 

birth (4 percent) and for women 35 years and older having 

their first orsecond child (5–8 percent) .Therate ofchildbearing for women aged 35 years and older has increased substantially during the past few years, with sizable increases in 

the proportion of mothers who are college graduates. 

Educational attainment of mother 

Women with the highest levels of schooling are the least 

likely to bear a low-birth-weight baby (table F). In 1985, 

mothers with only 9–11 years of schooling were 2.2–2.3 

times as likely to have an LBW, MLBW, or VLBW infant 

as were women with 16 years of schooling or more. The 

slightly lower LBW, MLBW, and VLBW rates for women 

with O-8 years of schooling than for women with 9–11 years 

of schooling reflect higher rates of fetal death for the least 

educated women, an indication that a higher proportion of 

pregnancies for such women result in fetal death rather than 

in a live LBW baby (7). Also, a substantial proportion of 

foreign-born Asian and Hispanic mothers, whose births are 

generally at low risk for LBW, have less than 9 years of 

schooling (8,9). 

The reduction in low, moderately low, and very low 

birth weight with increased schooling is distinctly less pronounced for black than for white babies. For example, the 

10


VLBW rate in 1985 for white babies whose mothers had 

9–11 years of schooling (13.4 per 1,000) was 1.9 times the 

rate for white mothers who had 16 years of schooling or 

more (7.0), but the VLBW rate for the less educated group 

was only 1.2 times as high as that for the more educated 

group among black mothers (28.6, compared with 23.6). 

For each level of schooling, black mothers have far higher 

levels of LBW, MLBW, and VLBW than do white mothers— 

and this racial differential in rates increases with added years 

of schooling. One possible explanation for this disparity is 

that black mothers have a lower average family income than 

do white mothers with comparable levels of education. Data 

from the 1983 National Health Interview Survey of the National 

Center for Health Statistics indicate that white women who 

had graduated from college had higher family incomes than 

did black women with similar levels of education (10). 

Between 1980 and 1985, the risk of low birth weight 

declined by 4 percent for mothers with at least 16 years 

of schooling but stayed virtually the same or increased for 

women with less education (table 4). 

The number of years of schooling a mother has completed 

correlates highly with a number of other variables discussed 

in this report (race, age, marital status, and interval between 

births). However, there is an inverse relationship between 

educational attainment and low birth weight, independent of 

race, age, birthplace, or marital status of mother or timing 

of prenatal care (7). A recent study of maternal weight gain 

during pregnancy found that the more years of schooling 

the mother had completed, the higher her weight gain was 

likely to be and, in turn, the higher the weight gain, the 

lower the risk of low birth weight (1 1), Thus, inadequate 

nutrition of less educated women may be one explanation 

for their greater risk of bearing an LBW infant. Additionally, 

better educated women have, on the average, a longer interval 

between live births, which also reduces the risk of LBW, 

as discussed in the next section. 

Other factors noted by researchers that help to explain 

the more favorable birth weight for babies of better educated 

women include their lower prevalence of heavy smoking during 
----

---

-- -- ----- ----- --

-- ---

--- ---- ----

l,ooo---

900----

800 

700---- — Low birth weight 

600----

——— Verylow birth weight 

500----

400----

300----

200----

150---- Black 

1oo---

90---

80--- White 70 

60---

III 50--- ~ 

n . .$. 40.- -

,, 

0 

0 ‘-

0“ 30-- : \ -———— —- —-- - \ ---_& .— -‘- Black 

&

n \

\ a 

~ 20-- - \ 

cc \ 

\ 

\ 

\ 

\\ 

-\\ -<- White 

lo- . \\\ /+ ,, N+ -~”- 9- . ,, 

-+. . . ‘, 8 -

.7- . ., 

6- . ,. 

5- .’ 

‘4 - . , 

3- . 

2- . 

.’ 

1-. t I I I I I 1 

Under 15-19 20-24 25-29 30-34 35-39 - 40+9 

15 years years years years years years years 

Age of mother 

NOTE: Low birth weight is weight less than 2,500 grams (5 pounds 8 ounces); very low birth weight is less than 1,500 grams (3 pounds 4 ounces). 

Figure 4. Rates of low and very low-birth weight by age of mother, for white snd blackbirths UnitedStateaj1985 ‘. 

,. 

pregnancy and their higher average heigh~ both of these factors Interval since last Iiie birth 

are associated with a higher birth weight (12-14). 

, In both 1980 and 1985, the birth certificates of California, There is a substantial difference in the risk of low birth 

Texas, and Washington did not include educational attainment weight between babies born less than 18 monihs after a previof the mother. ous live birth and births spaced further apart (table G). Babies 

11 
I40 

120 

I 00 

80 

60 

40 

0 

0-6 years 

NOTE: Excludes data for California, Texas, and Washington, which 

(5 pounds 8 ounces), 

Age 

— 20-24 years 

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

-------30-34 years 

— .—. — 35–39 years 

——— 40-49 years 

9–1 1 years 12 years 13–15 years 16 years or more 

Years of school completed 

did not require reporting of educational attainment of mother. Low birth weight ia weight less than 2,500 grams 

Figure 5. Rates of low birth weight, by educational attainment and age of mother: Total of 47 reporting States and the District of Columbia, 1985 

Table F. Rates of low, moderately low, and very low birth weight by educational attainment of mother and race of child: Total of 47 reporting Statea and 

the District of Columbia, 1985 

Low birth weight’ Moderately low birth weight2 Very low bitih weight3 

Years of school completed All races’ White Black All races4 White Black All races4 White Black 

Rate per 1,000 live births 

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69.0 56.7 124.9 56.5 47.3 98.0 12.5 9.4 26.9 

0-6years . ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.1 82.1 136.0 77.0 68.5 109.6 16.2 13,6 26.5 

9-n years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.4 83,9 145.6 83.7 70.5 117.0 17.7 13.4 28.6 

12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68.4 56,6 121.6 56.1 47.4 95.5 12.2 9,2 26.1 

13-15years . . . . . . . . . . . . . . . . . . . . . . . . 55.9 46.4 106.1 45.7 38.9 81.4 10.2 7.5 24.7 

16yearsormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45.3 40.5 94.9 37.0 33.5 71.2 8.2 7.0 23.6 

‘Leas thsn 2,500 grsms (5 pounds S ounces).


21,500-2,499 grama (3 pounds 4, ounces to 5 pounds 8 ounces),


3Leaa than l,500grama (3pounds40unces).


4hvAudea raceaothar than white and black,


51ncludes births with educational attainment of mother notatated.


NOTE: Excludes data for Cab fornia, Texaa, and WasMngton, wNchtid notrequim repoting ofeducational aKtinmentof mother,


born within 1 year after the previous live birth were 4.7 birth. These births also have ahigher risk of low birth weight 

times as likely to have a low birth weight as were babies than do those spaced at the optimum interval of 24 years 

born within an interval of2A years (206.9 per l,OOO,com- (73.9, compared with 44.3). It has been suggested that a 

pared with 44. 3). However, only about 2 percent of all second short time between pregnancies is related to intrauterine imor higher order births occur within 1 year after the previous poverishment, because there is insufficient time for the restorative birth. An additional 11 percent of second and higher tion of maternal nutrients necessary for adequate fetal 

order births occur within 1–11/2 years after the previous live development (15). 

12 
Table G. Rates of Iow, moderately low, andve~low Mtihweigh$ byintewal since l=t~wetitih andm@of cMld:Total of49re~ting States andthe 

Distriotof Columbiq 1985 

Low birth weight’ Moderate/y low birth weight2 Very low birth weight3 

Interval since last live birth All racesh White Black All races4 White Black All races4 White Black 

Rate per 1,000 five births 

All second and higher order births5,6. . . . . . . . . . . . . . . . . 57.9 45.7 116.0 47.7 38.2 92.3 10.2 7.4 23.6 

Lessthan 12months6 . . . . . . . . . . . . . . . . . . . . . . . . 206.9 166.2 300.5 135.7 113.9 185.9 71.2 52.4 114.6 

12-17 months . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.9 57.9 131.7 61.5 4&3 109.1 12.4 9.6 22.6 

18-23 months . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49.6 39.3 104.8 41.7 33.2 86.2 7.9 6.1 18.6 

24-47 months . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44.3 35.9 98.5 37.5 30.7 81.2 6.8 5.1 17.3 

48monthsormore . . . . . . . . . . . . . . . . . . . . . . . . . . 61.5 49.4 110.3 51.5 42.1 68.7 10.1 7.3 21.5 

lLess than 2,500 grams (5 pounds S ounces).


21,500-2,499 grams(3 pounds4 ouncesto 5 poundsS ounces).


‘Less than 1,500 grams (3 pounds 4 ounces).


41ncludes races 0th6r than white and black.


51ncludes bhthswith interval not stated.


%xcludes birthswith zero-month interval (multiple births).


NOTE =cludesdata for Texas, wtichtid notrquire re~ting ofdateof l~tlive Mfih. 

Although the risk of LBW, MLBW, and VLBW increases 

substantially for shortened birth intervals for both white and 

black births, the increase in risk is less for black than for 

white babies. For example, white babies born within an interval 

of 1–1% years are about 60 percent more likely to have 

a low birth weight than are those born within 24-47 months 

after the previous live birth; the comparable differential for 

black births is only 34 percent. 

However, there are several confounding factors to consider 

when examining the relationship between birth interval and 

birth weight. Intervals of less than 12 months include babies 

born prematurely, who are, as previously indicated, far more 

likely to have a low birth weight than are full-term newborns. 

Another confounding factor is the possibility of an intervening 

i%tal death between any given birth and the previous live 

birth, which may also adversely affect birth weight because 

of the shortened interpregnancy interval. Table H shows the 

risk of LBW, MLBW, and VLBW for full-term births for 

which the outcome of the preceding pregnancy was a live 

birth, with no intervening fetal deaths. For intervals of less 

than 1 year, the LBW rate was 65.6 per 1,000, 3.3 times 

the rate for intervals of 24-47 months (19.6); for intervals 

of 12–17 months, the rate was 33.2, 1.7 times the rate for 

intervals of 24-47 months. Even larger differentials by interval 

are evident for rates of very low birth weight. 

One reason for the elevated risk of LBW for younger 

mothers having a second or higher order birth (as noted previously) is the large proportion of closely spaced births for 

this age group. In 1985, 35 percent of second-order full-term 

births, 47 percent of third-order full-term births, and 61 percent 

of fourth-order full-term births to teenagers occurred within 

1Y2 years after the previous live birth. 

In a previous study of birth spacing (16), it was found 

that the elevation in low birth weight associated with closely 

spaced births could not be attributed solely to the fact that 

women with shorter birth intervals are also more likely to 

be young or to have low educational attainment. These more 

current data also indicate that for both white and black births, 

regardless of the mother’s marital status, age, or years of 

school completed, the percent of low birth weight for full-term 

Table H. Rates of low, moderately low, and very low birth weight for fullterm birthsj by interval since last Iiie birth and race of child Total of 49 

reporting States and the Distrfst of Columbi~ 19S5 

Moderate/y Very 

Low low low 

Interval since last live birth bitih birth birth 

and race of child weight’ weight2 weight3 

Rate per 1,000 five births 

All second and higherorder births4,a. . . . . . 24.7 24.0 0.7 

Lessthan12monthss . . . . . . . . . . . . . 65.6 61.9 3.8 

12-17 months . . . . . . . . . . . . . . . . . 33.2 32.2 0.9 

18-23 months . . . . . . . . . . . . . . . . . 21.4 20.8 0.6 

24-47 months . . . . . . . . . . . . . . . . . 19.6 19.1 0.5 

48months ormore . . . . . . . . . . . . . . . 27.6 26.8 0.8 

Whites . . . . . . . . . . . . . . . . . . . . . 19.6 19.1 0.5 

Lessthan12months5 . . . . . . . . . . . . . 50.5 47.9 2.7 

12-17 months . . . . . . . . . . . . . . . . . 25.8 25.1 0.7 

16-23 months . . . . . . . . . . . . . . . . . 17.0 16.5 0.5 

2447 months . . . . . . . . . . . . . . . . . 16.0 15.6 0.4 

43months ormore . . . . . . . . . . . . . . . 22.3 21.8 0.6 

Black . . . . . . . . . . . . . . . . . . . . . . 52.7 51.0 1.7 

Leasthan12months5 . . . . . . . . . . . . . 106.6 99.7 6.8 

12-17 months . . . . . . . . . . . . . . . . . 62.8 60.9 1.8 

16-23 months . . . . . . . . . . . . . . . . . 48.0 47.1 0.9 

24-47 months . . . . . . . . . . . . . ..’.. 46.2 44.9 1.3 

48months or more . . . . . . . . . . . . . . . 51.2 49.4 1.7 

lLass than 2,500 grams (5 pounds 8 ounces).


21,500-2,499 grams (3 pounds 4 ounce3 to 5 pounds 8 ounws).


3Less than 1,500 grams (3 pounds 4 ounce6).


41ncludes racea other than white and black and births with interval not siated,


5Excludes births with zero-month intewal (multiple births).


NOTE Excludes data for Texas, which did not require reporting of date of last live birth or


fetal death. Full-term birlhs are births of 37 weeka of gestation and over. Excludes live bhths


where there was an intervening fetal death following the previous live bhth.


births is highest for intervals of less than 18 months (figures 

6 and 7-data not shown for marital status). 

In 1985, only the birth certificate of Texas did not include 

the date of the last live birth, which is the basis for determining 

the interval since the last live birth. 

Marital status of mother 

In 1985, the rate of low birth weight for births to unmarried 

women was about twice that for births to married women 

13 
.

80


r


Age of mother 

., ,.., 

Under,20 years 

20-24 years 

25-29 years 

,.. 30 years and over 

! 

al 

g 

0 

0 

0. o I I I I [ 

80 

60 

40 

20 

0 

1 

... . . . ,, :., .,,, .,.. ,.-1.. < 

Years of school completed L 

i, 

9–1 1 years 

O-8 years 

12 ye;rs 

13 ye~rs or 

7,, 

I I I I I 

Less than 12-17 18-23 24-47 48 months 12 months months months months or more 

Interval since last live birth 

NOTE: Excludes tive births where there was an intewening fetal deathfollowing the previous fiva bfr&h. Figures for aga of mother exclude data for Taxas,,which did,notjnclude ‘date of 

Iksl Ihe birth or last fetal death on the tjtih @mfic& Hgures for eduoafi~nal a~nment ex~[ude data for Cahforiia, Texss, and Wasfjngton, ~~~h ~d not include t~~ item & the ljrth 

certificate. Low birth weight is weight less than 2,500 grams (5 pounds S ounces). Full-term births are births of 37 weeks of gestation or longer. 

Figure 6. Rates of low birth weight for full-term whKe births, by interval dnce last Iiie birth, age, and educational attainment of mother: Total of reporting 

areas. 1965 

(109.4 per 1,000, qunpared with 55.7) (table J). However, 

the difference in rates by marital status is considerably smaller 

for black than for white births. The rate of LBW was 68 

percent higher for white unmarried mothers than for white 

married mothers (86.0, compared with 51. 3) but only 39 

14 

,,; ,.,, ,,, :C) 

,, ,. ’’.’.. ,. ,; 

. .. . . 

percent higher for unmarried than for married <blackmothets 

(139.9, compared with 100.5). This difference by’ mtiital” 

status is even more pronounced for VLBW, but only for 

white mothers. 

Much of the difference in the incidence of low birth 
150 

Age of mother 

[ 

.2 

‘E.-

J1 0 I I 1 I ! 

al 

~ 

0 

0 

0-

&l Years of school completed 

n 

0 150 5 

u 

“1 

100 

9-11 years 

O-8 years 

50 —- 12 years 

13 years or more 

01 I 1 I t I 

Less than 12-17 18-23 24-47 48 months 

12 months months months months or more 

Interval since last five birth 

NOTE Excludes five births where there was an intervening fetal death following the previous live birth. Figures for age of mother exclude data for Texas, whish did not include date of 

last live birth or last fetal death cm the birth cerfifisate. Figures for educational attainment exclude data for California, Texas, and Washington, which did not include this item on the birth 

cartificale. Low birth weight is weight leas than 2,500 grams (5 pounds 8 ounces). Full term birlhs are births of 37 weeks of gestation or 10ng3r. 

F~ure 7. Rates of low birth weight for full-term black birfhs, by interval since last live birth age, and educational attainment of mother: Total of reporting 

areas, 198S 

15 
Table J. Rates of low, moderately low, and very low birth weight, by marital status of mother and race of child: United States, 1985 .,, 

Low birth weight’ Moderately low birth weight2 Very low bkth weight3 

Marital status of mother All races” White Black All races4 White Black All races4 White Black 

Rate per 1,000 live birlhs 

Total, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67.5 56.4 124.2 55.4 47.0 97.6 12.1 9.4 26.5 

Married . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . 55.7 51.3 100.5 46.2 43.0 76.2 9.5 8.3 22.2 

Unmarried . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109.4 66.0 139.9 67.8 70.4 110.5 21.5 15.5 29.4 

lLess than 2,500 grams (5 pounds 8 ounces).


21,500-2,499 grams (3 pounds 4 ounces to 5 pounds 8 ounces)


3Less than l,500grsms (3 pounds 40unces).


41ncludes races other than whie and black,


weight by marital status can be explained by the generally 

younger ages and lower educational attainment of unmarried 

women. However, ahigher risk of LBWfor out-of-wedlock 

births, even when demographic and socioeconomic differences 

are taken into account, has been observed for some time 

(7). A potent reason for the higher risk of LBW for unmarried 

than for married mothers with equivalent years of schooling 

is that they smoke more than married mothers at all levels 

of educational attainment ( 13). 

As shown in figure 8, white unmarried mothers are far 

more likely than white married mothers of matched educational 

attainment to bear a low-birth-weight baby. Differentials in 

LBW by marital status for equivalent years of schooling are 

smaller, but still quite substantial, for black mothers. 

Although the risk of low birth weight declined for both 

married and unmarried mothers between 1980 and 1985, the 

decline was greater for unmarried women (6 percent, compared 

with 4 percent) (table 4). In this period, LBW rates declined 

by 3 percent for white married mothers and by 5 percent 

for white unmarried mothers, but by only 2 percent for black 

married and unmarried mothers. One explanation for the large 

decline in risk of LBW for unmarried mothers is that the 

proportion of unmarried mothers who were in their teens 

declined during this period, from 41 percent to 34 percent. 

Also, the proportion of unmarried mothers who had completed 

12 years or more of schooling increased from 50 to 55 percent. 

However, in 1985, the LBW rate for white unmarried mothers 

with at least 12 years of schooling was still about 80 percent 

higher than for white married mothers (84. 8, compared with 

46. 8) and nearly 40 percent higher for unmarried than for 

married black mothers with this level of educational attainment 

(132.2, compared with 96.8). 

There is also a substantial racial differential in the incidence of LBW for both unmarried and married mothers. Black 

unmarried mothers were 1.6 to 1.9 times as likely to bear 

an LBW, MLBW, or VLBW infant as were white unmarried 

mothers. The racial differential is even greater for married 

mothers. The risk of LBW or MLBW was 1.8 to 2.0 times 

as high for black as for white married mothers. The risk 

of VLBW was 2.7 times as high for married black as for 

married white mothers (table J). 

Prenatal care 

Whether there is an association between when a woman 

starts prenatal care and low birth weight is difficult to ascertain, 

because when prenatal care begins is related to other factors 

that affect birth weight. Women at high risk of delivering 

an LBW baby—those who are young, unmarried, or with 

little education—are more likely to delay prenatal care (17). 

Also, women who deliver prematurely may have started care 

early in pregnancy, although their babies are far more likely 

than others to have a low birth weight because of their shortened 

gestation. This in effect biases the comparison of the risk 

of low birth weight between women starting care early and 

those who start care in the third trimester of pregnancy, because 

the latter group includes only women with full-term births. 

Table K shows the risk of LBW, MLBW, or VLBW 

according to month prenatal care began for births at gestational 

ages of at least 37 weeks. All of these births were to mothers 

whose pregnancies lasted long enough that they could begin 

care as iate as the third trimester. It is evident that the likelihood 

of LBW, MLBW, or VLBW increases as care is delayed 

for both white and black full-term births. The risk of such 

adverse outcomes is almost twice as high for mothers starting 

care in the third trimester as for mothers beginning care”in 

the first or second month of pregnancy. However, the increase 

in all LBW rates with delayed care is not generally as pronounced for black as for white full-term births. In addition, 

at comparable levels of care, black babies are far more likely 

to have an LBW, MLBW, or VLBW outcome than are white 

babies. For example, when prenatal care started in the first 

through third months of pregnancy, black babies were 2.3–2.4 

times as likely as white babies to weigh less than 2,500 grams. 

During the 1981–85 period, there was a decline in the 

rate of low birth weight for all levels of prenatal care (table L). The decline was 5-6 percent for care beginning in 

the first or third trimester of pregnancy and 9 percent for 

care beginning in the second trimester. However, although 

there was also a substantial decline (11 percent) in the LBW 

rate for mothers who did not receive any prenatal care, the 

1985 LBW rate for these mothers was still at least two-thirds 

higher than the rate for any group who received care. 

16 
180 

160 

140


Black, unmarried 

Black, married 

White. unmarried 

60 

— 40 White, married 

O-8 years 9-11 years 12 years 1>15 yeara 16 years or more 

Years of school completed 

NOTE. Excludes data for California, Texas, and Washington, which did not require reporting of educational attainment of mother. Low bhlh weight ia weight leas than 2,500 grama 

(5 pounds 8 ounces). 

Figure 8. Rates of low birth weight for women aged 20 years and over, by educational attainment and marital status of mother and race of child 

Total of 47 reporting States and District of Columb& 1985 

Table K. Rates of low, moderately Iow, and very low birth weight for full-term births by month of pregnancy prenatal oare began and race of child: 

United Stateaj 1985 

Low birth weight’ Moderately low birth weightz Very /ow bihh weight3 

Month of pregnancy prenatal care began All races4 White Black All races4 White Black All races4 White Black 

Rate per 1,000 five births 

Tota15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.0 25.0 57.9 29.1 24.3 55.7 0.9 0.7 2.2 

lstand2d month . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.6 21.3 50.3 24.0 20.7 48.8 0.7 0.6 1.5 

3d month . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.1 25.2 57.1 29.3 24.5 55.1 0.9 0.6 2.0 

4th-6th month . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38.5 32.1 60.1 37.5 31.2 58.3 1.1 0.9 1.9 

7th-9th month . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46.3 38.8 69.1 44.7 37.8 66.1 1.6 1.1 3.0 

No prenatal care . . . . . . . . . . . . . . . . . . . . . . . . . . . 78.3 81.9 115.4 72.5 58.0 105.0 5.8 3.9 10.4 

‘Leas than 2,500 grama (5 pounds E ounces).


21,500-2,499 grams (3 pounds 4 ounces to 5 pounds 8 ounces).


‘Less than 1,500 grams (3 pounds 4 ounces).


41ncludesrams other than white and black.


51ncludeabirths with month of pregnancy prenatal care began not stated.


NOTE Full-tarrnbirths are bhthsof37w eefGofg estationandover.


17

Table L. Rates oflowbtih weight for full-tern ti~hs, bymonth ofpregnancy prenatal ~rebegan andrace ofcMld: Totilof 49repoting S,qt,ea andthe,, 

Oiatrict of Columbia, 1981, and United States, 1985 ,.. 

All races~ White Black 

Month of pregnancy prenatal care began 2 1981 1985 1981-85 1981 1985 1981-85 1981 1985 1981-85 

Rate per Percent Rate per Percent Rate per Percent 

l,OOO1ive births change 1,000 live births change 1,000 live births change 

lstand2d month . . . . . . . . . . . . . . . . . . . . . . . . . 26.1 24.6 -5.7 22.6 21.3 -5.8 52.3 50.3 -3.8 

3d month . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.7 30.1 -5.0 26.7 25.2 L 5.6, 59.6 57.1 -4,5 

4th-6th month . . . . . . . . . . . . . . . . . . . . . . . 42.2 38.5 -6.6 34.4 32.1 -6.7 67.6 60.1 – 11.4 

7th-9th month . . . . . . . . . . . . . . . . . . . . . . . . 46.8 46.3 -5.1 39.4 38.8 -1.5 76.4 69.1 -9.6 

No prenatal care . . . . . . . . . . . . . . . . . . . . . . . 86.2 78.3 –11.2 66.6 61.9 -10.0 130.6 115.4 –11.6 

Ilncludes racea other than white and black.


2Refers only to full-term births (37 weeks ofgeatation and over).


NOTE For1981, excludea data for New Mexico, wMchtid notrwuire repoting ofdateof l=tnomal menstwal period. bw@~weight iaweight leas than 2,500grams (5pounda8 ouncea). ,, 

,, 

Table M. Obsemed andadjusted rates oflow, mtierate~low, andve~low titihweight fortilFtem Mtihs, bymonth ofpregnan~ prenatd~rebegan 

andrace ofcMld: Total of47repoting States andthe Ustnctof Columbia, 1985 

Low birth weightl Moderately low bi~h weightz Very low birth we&ht3 

Month of pregnancy prenatal care began and race of child Obsewed A@sted4 Observed “A@usted4 Observed A@usted4 

All races 5 Rate per 1,000 live births 

lst–2d month . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.0 25.0 24.4 24.4 0.7 0.7 

3d month . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.7 28.2 29.9 27.5 0.8 0.8 

4th-6th month . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40.0 34.6 36.9 33.6 ‘1.1 1.0 

7th-9th month . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49.2 41.5 47.4 39.6 1.8 1.8 

No prenatal care, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86.5 68.5 79.4 63.1 7.1 5.4’ 

White 

lst-2d month.......,,.. . . . . . . . . . . . . . . . . . 21.5 21.5 20.9 20.9 0.5 0.5 

3d month . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.5 23.5 24.9 23.0 0.6 0.6 

4th-6th month........,,. . . . . . . . . . . . . . . . . . . . . . . . 32.9 27.8 32.1 27.0 0<8 0.6 

7th-9th month . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40.9 33.7 39.6 32.7 1.3 0.9 

No prenatal care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67.6 51.9 62.6 47.6 4.9 ~ 4.3 

,, 

Black 

lS–2d month, . .,, . . . . . . . . . . . . . . . . . . . . . . . . . . . 50.9 50.9 49.3 49.3 1.6 1.6 

3d month . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57.3 55.0 55.3 53.1 1.9 1.9 

4th-6th month . . . . . . . . . . . . . . . . . . . . . . . . . . ...’. . . . . 60.2 57.4 58.4 55.5 1.9 1.9 

7th–9th month . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69.7 64.9 66.6 60.9 3.1 4.1 

No prenatal care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116.1 101.6 105.2 93.3 10.9 8.3 

‘Less than 2,500 grams (5 pounds S ounces), 

21,50C!-2,499 grams (3 pounds 4 ounces to 5 pounds S ounces). 

‘Leas than l,500grama (3pounda40unces). 

4Adjuated tore fleet the educational attainment of mothers who began prenafalcare in the latand2dmonthaof pregnancy. See appendix IV. 

%cludeara cesotherthsn white and black, 

NOTE: Excludes Mtihsto residen& of California, Texas, and Wasbngton, which didnotrequire repoting ofeducational apainment ofmotier. Full-tern tifihsare tidhsof 37weekaofgeakfion 

and over. 

Mothers who start care in the first timester of pregnancy 

have, on the average, higher levels of educational attainment 

than do mothers who delay care to the second or third trimester 

or mothers who receive no care. Thus, the lower incidence 

ofLBWwhen carestartsinearly pregnancyisto some extent 

areflectionof this higherproportion ofbettereducated women. 

If all mothers are assumed to have the same educational attainment as mothers who start care in the first or second month 

ofpregnancy, the incidence of LBW for women starting care 

Iatein pregnancyor receiving no careis reduced substantially 

(table M). 

Before adjustment for differences in years of schooling, 

the incidence of LBW was 97 percent higher for care starting 

in the third trimester than for care starting in the first or 

second month of pregnancy. After adjustment, this differential’ 

was66 percent. Although there are large reductions inLBW 

and MLBW incidence for both white and black births when 

educational attainment is taken into account, the reductions 

are relatively much greater for white births. Adjustment for 

differences in the mother’s educational attainment decreases 

the risk of VLBW for care starting in late pregnancy for 

white but not for black babies. For mothers having no prenatal 

care, LBW, MLBW, and VLBW rates are all reduced for 

both white and black babies after differences in educational 

attainment are eliminated. 

Although the differential is reduced, there still remains 

a substantial increase in theriskofLBW, MLBW, and’VLB’W 

whencareisdelayed orwhenthereis nocare. 

18 
Surimnary “ ~ “’”” “ 

, ,, . ‘.’. 

., 

#-

A Commo,n~e,rne,throughout this study is the substantial 

and persistent difference between black and white babies in 

the risk of low birth weight. In 1975, black babies were 

2,1 times as likely as white babies to have a birth weight 

of less thti 2,500 grams. Low’‘bitih weight declined more 

for white than for black births in the 1975–85 period, increasing 

the racial deferential to 2.2: ‘It remained at this level .in 1986 

and 1987. 

Although relatively more black than white mothers are 

represented in ‘subgroups at high risk of LBW (unmarried, 

less than 20 years of age, with less than 12 years of education, 

or with late or no care during pregnancy), this only partly 

explaiqs the greater risk of LBW for black babies. Regardless 

of age of mother, month prenatal care began, years of schooling 

completed, or marital status, black mothers are generally twice 

as likely to have an LBW baby and two to three times as 

likely to have aVLBW baby: 

Although increased years of schooling lowers the risk 

of low birth weight for both black and white babies in high-risk 

categories, the racial gap in LBW incidence actually increases 

with added years of schooling. 

One of the major reasons for the ,greater prevalence of 

low birth weight among black babies is their higher risk of 

being born prematurely. Although the incidence of low birth 

weight was only 7 percent higher for black than for white 

premature births in 1985, black babies were more than twice 

as likely to be born before 37 weeks of gestation (17.5 percent 

of black births, compared with 8.2 percent of white births). 

According to a recentiy published study of premature births 

in one Boston hospital, the lower maternal hematocrit of black 

mothers explained a substantial part of the higher black incidence of prematurity (18). Data from the National Health 

and Nutrition Examination Survey indicate that black women 

in the c“Klldbearingages, regardless of poverty status, have 

a significantly lower, hematocrit than do their white counter­

,, 

., 

,,. ,. 

,. .“ ., 1.. 

,,. ,, ,, 

,*, : 

,,. . ., ,“-. 

,.. 1 .,, i .,, ,. .’ 

;. ., ’...’ ,,, 

parts (19). However, much is still unknown about the causes 

of prematurity. 

The differential between black and white women in the 

risk of low and very low birth weight after controlling for 

“age, education, marital status, and prenatal. care may to some 

extent reflect differences in personal finances, health status, 

and lifestyle. Data from the 1982 National Survey of Family 

Growth indicate that sources of prenatal care differ substantially for black and white women. Fewer than half of black 

women receive care from a private doctor, compared with 

about 80 percent of white women (20). Black women are 

generally more likely than white women of similar prepregnancy weight to gain less than 16 pounds during their pregnancy (11). Black married women who have had at least one 

child are more likely to work during pregnancy than are white 

married women who have had the same number of children, ‘ 

and they are more likely to be blue-collar workers (21). As 

noted earlier, black mothers have a lower average family 

income than do whhe mothers at comparable levels of 

education (1O). 

There are undoubtedly many other racial differences in 

nutritional status, lifestyle, and environmental conditions, not 

yet quantified, that have an important impact on birth weight. 

Beginning with the 1989 data year, a wealth of new information 

relevant to the etiology of low birth weight will become available from the revised U.S. Certificate of Live Birth, to be 

implemented by almost all States in 1989. Included on the 

new certificate are questions relating to medical risk, factors 

of pregnancy, such as anemia and cardiac disease, and lifestyle 

factors—tobacco and alcohol use and weight gain during pregnancy-that are closely related to birth weight. This new 

information, combined with other socioeconomic and health 

data from the birth certificate, should help clarify the reasons 

for +e huge and persistent racial differenti~s in the incidence 

of low birth weight. 

. . . 

19

References


1.	 Hogue CJR, Buehler JW, Strauss LT, Smith JC. Overview 

of the National Infant Mortality Surveillance (NIMS) project— 

design, methods, results. Public Health Rep 102(2):126-38. 

1987. 

2.	 McCormick MC. The contribution of low birth weight to infant 

mortality and childhood morbidity. N Engl J Med 312:82-90. 

1985. 

3.	 Van den Berg BJ, Yerushalmy J. The relationship of the rate 

of intrauterine growth of infants of low birth weight to mortality, 

morbidity, and congenital anomalies. J Pediatr 69(4):53 145. 

1966. 

4.	 Taffel SM. A method of imputing length of gestation on birth 

certificates. National Center for Health Statistics. Vital Health 

Stat 2(93). 1982. 

5.	 Kessel S, Villar J, Berendes HW, Nugent RP. The changing 

pattern of low birth weight in the United States. JAMA 

251(15):1978-82, 1984. 

6.	 Geronimus AT. Onteenage childbearing andneonatal mofiality 

in the United States, Population and Development Review 

13(2):245-79. 1987. 

7.	 Taffel SM. Factors associated with low birth weight, United 

States, 1976. National Center for Heakh Statistics. Vital Health 

Stat 21(37). 1980. 

8.	 Taffel SM. Characteristics of Asian bifihs: United States, 1980. 

Monthly vital statistics report; vo132no 10, suppl. Hyattsville, 

Maryland: Public Health Service. 1984. 

9.	 Ventura SJ, Taffel SM. Childbearing characteristics of U.S. 

and foreign-born Hispanic mothers. Public Health Rep 100 

(6):647-52. 1985. 

10.	 Kleinman JC, Kessel SS. Racial differences in low birth weight. 

N Engl J Med 317(12):749-53. 1987. 

11.	 Taffel SM. Maternal weight gain and the outcome of pregnancy, 

United States, 1980. National Center for Health Statistics. Vital 

Health Stat 21(44). 1986. 

12.	 Kleinman JC, Kopstein A. Smoking during pregnancy, 1967–80. 

Am J Public Health 77(7):823–25. 1987. 

13.	 Kleinman JC, Pierre MB, Madans JH, et al. The effects of 

maternal smoking on fetal and infant mortality. Am J Epidemiol 

127(2):27482. 1988. 

14.	 Kleinman JC, Madans JH. The effects of maternal smoking, 

physical stature, and educational attainment on the incidence 

of low birth weight. Am J Epidemiol 121(6):843-55. 1985. 

15.	 Honey WL, Rosenbaum AL, Churchill JA. Effect of rapid 

succession of pregnancy. In: Prenatal Factors Affecting Human . 

Development. Scientific Publication No. 185. Washington: Pan 

American Health Organization, 41-4.1969. 

16.	 Spratley E, Taffel SM. Interval between births: United States, 

1970-77. National Center for Health Statistics. VitaI Health 

Stat21(39). 1981. 

17.	 Taffel SM. PrenataI care-United States, 1969-1975. National 

Center for Health Statistics, Vital Health Stat 21(33). 1978. 

18.	 Lieberman E, Ryan KJ, Monson RR, Schoenbaum SC. Risk 

factors accounting for racial differences in the rate of premature 

birth. NEnglJMed317(1 2):743-48. 1987. 

19.	 Fuilwood R. Hematological and nutritional biochemistry reference data for persons 6 months-74 years of age: United States, 

1976-80. National Center for Health Statistics. Vital Health 

Stat 11(232). 1982. 

20.	 Pamuk ER, Mosher WD. Health aspects of pregnancy and 

childbirth. National Center for Health Statistics. Vital Health 

Stat23(16). 1988. 

21.	 Makuc D. Employment characteristics of mothers during pregnancy. Health, United States, 1983. National Center for Health 

Statistics. Washington: Public Health Service. 1983. 

22.	 Berkov B. An evaluation of California’s inferred birth statistics 

for unmarried women. National Center for Health Statistics. 

Vital Health Stat 2(97). 1985. 

20 
List of detailed tables


1.	 Rates of low, moderately low, and very low birth weight, 4. Rates of low birth weight, by age, educational


by race of child: United States, 1975-87 . . . . . . . . . 22 attainment, and marital status of mother and race of child


2. Rates of low, moderately low, and very low birth weight, Total of reporting areas, 1980 and 1985 . . . . . . . . . 25


by period of gestation and race of child: Total 0[ 49 5. Rates of low, moderately low, and very low birth weight, 

reporting States and the District of Columbia, 1981, and by age of mother, live-birth order, and race of child:


United States, 1985 . . . . . . . . ..- . . . . . ...23 United States, 1985 . . . . . . . . . . . . . . . . ...25


3.	 Rates of low, moderately low, and very low birth weight,


by age and educational attainment of mother and race of


child: Total of 47 reporting States and the District of


Columbia, 1985 . . . . . . . . . . . . . . . . . . ...24


21

Table 1. Rates of low, moderately low, and very low birth weigh$ by race of CIIM IJntied stat+; 1975+s7, , .. , ,. .	 ( ~ ,,” 

,. ,,, 

Low birth weight’ Moderate/y low birih weight2 Very low birth weight’ 

Year All races 4 White Black All rsces4 White Black All races 4 White Black 

. . ,, ,’. 

1975 

1976 

1977 

1978


1979


1980 

1981 

1982


1983


1984


1985


1986 . . . . . . . . . . . . . . . . . . . . . . . . . .


1987 ,., ,. . . . . . . . . . . . . . . . . . . . . . .


1975-60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

1960-85 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

1985-67 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

lLesslhan 2,500 grams (5pcimds80unces).


21,500-2,499 grams (3 pounds 4 ounces to 5 pounds 8 ounces),


aLess than 1,500 grams (3 pounds 4 ounces).


41ncludes ram other than whtie and black.


73.9 62.6 130.9 

72.6 61.3 129.7 

70.7 59.3 127.9 

71.1 59.4 126.5 

69.4 5,6.0 125.5 

66.4 57.0 124.9 

68.1 56.7 125.3 

67.5 56.3 124.0 

66.2 56.7 125.9 

67.2 55.9 123.6 

67.5 56.4 124.2 

88.1 56.4 125.3 

89.0 56.6 127.1 

– 7.4 – 8.9 – 4.6 

–1.3	 –1.1 -0.6 

2,2 0.7 2.3 

Rate per 1,000 live births 

62.3 53.4 107.2 

61.1 52.2 105.6 

59.4 50.5 104.2 

59.4 50.3 104.2 

57.9 46.9 101.8 

56.9 46.1 100.5 

56.5 47.7 100.6 

55.8 47.1 96.9 

56.3 47.4 100.4 

55.3 46.7 98.1 

55.4 47.0 97.6 

56.0 47.2 96.6 

56.6 47.4 99.6 

Percent change 

-8.7 -9.9 – 6.3 

–	 2.6 – 2.3 – 2.9 

2.2 0.9 2.3 

11.6 9.2 23.7 

11.5 9.1 24.0 

11.3 8.9 23.6 

11.7 9.1 24.3 

11.5 9,0 2$.7 

11.5 9.0 24.4 

11.6 9.0 ,24.7 

11.8 9.2 25.? 

11.9 9.3 25.5 

‘11.9 9.2 ,25.6 

12.1 9.4 26.5 

12.1 9.3 26.6 

12.4 9:4 27.3 

-0.9 -2:2 

5.2 t q:4 :;: , 

2.5 -“.: 3.6 ‘. ,,. 

,, 

,, 

..-, 

!, 

,, 

!, 

., 

,,, 

,,. ,, 

,, 

22 
Table2. Rates of low, moderately low, andvery low birth weigh$ bypenod ofgeshtin andmceof chfld:Totd of49repoting States andthe Mstnctof 

Columbia 1981, and United State% 1985 

Low birth weight’ Moderately low birth weight2 Very low birth weight3 

Period of gestation and race of child 198? 1985 1981-85 1981 1965 1981-95 1981 1985 1981-85 

Rate per Percent Rate per” Percent Rate per Percent 

1,000 live births change 1,000 live births change 1,000 live births change 

Allraces4 . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . 68.1 67.5 -0.9 56.5 55.4 –1.9 11.6 12.1 4.3 

Under 28weeks . . . . . . . . . . . . . . . . . . . . . . . . . . 777.5 768.0 –1.2 107.9 99.5 -7.8 669.6 668.5 – 0.2 

28-31 weeks . . . . . . . . . . . . .. . . . . . . . . . . . . . . 666.8 662.8 -0.9 335.2 333.7 – 0.4 333.5 329.2 –1.3 

32-35weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . 411.5 406.7 – 1.2 378.7 373.5 -1.4 32.8 33.2 1.2 

36weeks . . . . . . . . . . . . . . . : . . . . . . . . . . . . . 196.3 197.2 0.5 190.1 191.2 0.6 6.2 6.0 -3.2 

37-39weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . 50.0 46.6 -6.8 48.8 45.4 – 7.0 1.2 1.2 

40weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.6 17.3 –11.7 18.6 16.8 -10.6 0.7 0.6 – 14.3 

41 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.6 14.6 – 12.0 15.6 14.0 – 10.3 1.0 0.6 -40.0 

42weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4 21.0 – 6.3 21.3 19.9 – 6.6 1.1 1.1 —

Under37weeks . . . . . . . . . . . . . . . . . . . . . . . . . 397.7 394.2 -0.9 292.0 287.5 -1.5 105.8 106.8 0.9 

37weeksand over . . . . . . . . . . . . . . . . . . . . . . . . 32.0 30.0 -6.3 31.0 29.1 – 6.1 1.0 0.9 – 10.0 

White . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56.6 56.4 -0.4 47.5 47.0 -1.1 9.0 9.4 4.4 

Under28weeks . . . . . . . . . . . . . . . . . . . . . . . . . 780.9 767.0 -1.8 87.5 82.9 -5.3 693.4 684.1 -1.3 

26-31 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . 694.8 683.2 –1.7 345.3 341.5 –1.1 349.5 341.6 – 2.3 

32-35weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . 422.9 418.9 – 0.9 391.0 387.0 –1.0 31.8 31.9 0.3 

36weeks . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . 167.0 190.6 1.9 181.4 185.3 2.1 5.6 5.3 – 5.4 

37-39weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.1 40.2 – 6.7 42.1 39.3 – 6.7 0.9 0.9 — 

40weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2 14.1 – 13.0 15.7 13.6 -13.4 0.5 0.4 – 20.0 

41 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2 11.7 -11.4 12.5 11.2 – 10.4 0.7 0.5 -28.6 

42weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.7 17.2 – 2.8 16.9 16.4 -3.0 0.8 0.8 

Under37weeks . . . . . . . . . . . . . . . . . . . . . . . . . 392.2 389.0 – 0.8 293.3 290.6 -0.9 98.9 98.4 -0.5 

37weeksand over . . . . . . . . . ’. . . . . . . . . . . . . . . 26.4 25.0 -5.3 25.7 24.3 – 5.4 0.8 0.7 -12.5 

Black . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125.3 124.2 -0.9 100.6 97.6 – 3.0 24.7 26.5 7.3 

Under28weeks . . . . . . . . . . . . . . . . . . . . . . . . . 774.9 772.5 – 0.3 138.9 122.5 -11.8 636.0 650.0 2.2 

26-31 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . 631.6 636.4 0.8 321.8 323.6 0.6 309.8 312.8 1.0 

32-35weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . 395.1 391.9 -0.8 356.8 354.4 –1.2 36.4 37.5 3.0 

36weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226.9 221.1 – 2.6 218.9 212.4 – 3.0 8.0 8.7 8.8 

37-39weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . 60.7 76.5 – 5.2 76.6 74.2 -5.6 2.1 2.3 9.5 

40weeks . . . . . . . . . . . . . . . . . . . . . .’....... 40.5 38.4 -5.2 38.5 36.9 -4.2 2.1 1.5 – 28.6 

41 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40.9 35.1 – 14.2 37.7 33.4 –11.4 3.2 1.6 – 50.0 

42weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.2 43.8 -14.5 48.5 40.8 -15.9 2.7 3.0 11.1 

Under37weeks . . . . . . . . . . . . . . . . . . . . . . . . . 418.9 418.0 – 0.2 293.8 286.6 – 2.5 125.2 131.4 5.0 

37weeksandover . . . . . . . . . . . . . . . . . . . . . . . . 61.9 57.9 -6.5 59.6 55.7 – 6.5 2.3 2.2 – 4.3 

1Lsss than 2,500 grams (5 pounds 8 ounces). 

21,500-2,499grams (3pounds40unces to5pamds80unces). 

3Lasethsn 1,500 grams (3 rmunds 4 ounces). 

41ncludesrecesother than whtie and black. 

NOTE For1981, excludes dab for New Mexim, wNchddnot require repting of fimtday oflastnomal menstmal period. 

, ., 

23 
.

Table3. Rates of bw, mtierate~Iow, andve~low Mtihweigh4 bysgesnd edu=tional atinment ofmother andrace ofcMld Total of47repotiing 

States and the Diitrfot of Columbiaj 19S5 

Low birth weight’ Moderately low bitih weight2 Ve~ low birth weight3 

Age and yeara of school completed by mother All races’ White Black All races 4 White Black All races4 White Black 

Rate per 1,000 live births 

20-24 years ofage5 . . . . . . . . . . . . . . . . . . . . . . . . . 7~ .0 58.5 121.2 56.3 49.0 95.5 12.7 9.5 25.8 

0-6years . . . . . . . . . . . . . . . . . . . . . 86.2 79.8 129.4 73.2 67.9 108.1 13.0 11.9 21.3 

9-n years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95.6 81.1 143.0 79.9 68.9 115.5 15.8 12.1 27.5 

12years . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67.0 54.8 118.1 55.1 45.9 93.5 11.9 6.9 24.6 

13-15years . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56.4 44.7 101.4 45.6 37.3 77.5 10.8 7.4 23.9 

16yearsormore . . . . . . . . . . . . . . . . . . . . . . . . . 49.6 41.9 95.7 39.9 34.6 69.7 9.7 7.3 26.0 

25-29yearsofage5 . . . . . . . . . . . . . . . . 59.9 50.1 119.9 49.4 42.2 93.1 10.5 7.9 26.8 

0-6years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.7 67.7 111.1 64.0 58.6 92.7 10.7 9.1 16.4 

9-n yeara . . . . . . . . . . . . . . . . . . . . . . 103.5 84.6 160.4 86.0 72.4 127.8 17.4 12.2 32.5 

12years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.0 52.6 119.9 51.4 44.4 93.9 10.6 8.2 26.0 

13-15yeara . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.7 44.5 104.1 43.4 37.4 79.8 9.4 7.1 24.3 

16yearsormore . . . . . . . . . . . . . . . . . . . . . . . . . 41.9 36.8 92.7 34.4 30.8 69.0 7.5 6.1 23.6 

3C-84yearsofage5 . . . . . . . . . . . . . . . . . . . . . . . . . 61.1 52.0 124.3 50.0 43.3 96.0 11.1 8.7 28.4 

0-6years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.2 71.6 130.9 67.2 58.4 101.1 16.0 13.2 29.8 

Ef-llyear s . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.3 91.9 164.6 95.5 79.6 133.6 T7.8 12.3 31.1 

12years ... . . . . . . . . . . . . . . . . . . . . . . . . . . . 70.2 59.8 128.5 57.4 50.2 98.2 12.7 9.6 30.3 

13-15years . . . . . . . . . . . . . . . . . . . . . 55.7 47.9 112.5 45.9 40.2 86.9 9.6 7.6 25.6 

16yearsormore . . . . . . . . . . . . . . . . . . . 45.4 41.4 95.1 37.1 34.1 72.4 8.3 7.3 22.6 

35-39years ofage5 . . . . . . . . . . . . . . . . . . . . . . . 70.7 61.1 127.2 57.6 50.4 99.3 13.1 10.7 27.9 

0-6years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86.5 62.6 118.9 72.9 66.5 94.3 15.6 14.1 24.7 

6-n years . . . . .. . . . . . . . . . . . 121.8 105.5 158.7 101.0 87.6 130.0 20.7 17.7 26.7 \ 

12years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.9 70.5 133.3 66.9 58.8 103.9 15.0 11.7 29.4 

13-15years . . . . . . . . . . . . . . . . . . . . . . . . . . 66.1 57.9 118.2 54.0 47.9 90.8 12.1 9.9 27.4 

16yearaor more . . . . . . . . . . . . . . . 51.8 47.4 99.9 42.3 39.0 75.8 9.5 8.4 24.1 

40-49yearsofage5 . . . . . . . . . . . . . . . . . . . . . . . . 85.6 74.7 135.5 70.5 61.6 111.2 15.1 13.1 24.2 

0-6yeara . . . . . . . . . . . . . . . . . . . . 103.4 91.8 134.8 61.7 71.8 107.8 21.7 20.1 27.0 

g-n years . . . . . . . . . . . . . . . . . . . . 131.4 123.8 144.1 111.4 105.4 119.9 20.0 18.4 24.2 

12years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.7 79,1 148.2 76.7 67.1 119.3 15.1 12.0 28.9 

13-15years . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76.5 68.8 123.1 62.4 55.9 104.5 14.1 12.9 16.7 

16yearsormore . . . . . . . . . . . . . . . . . . . . . . . . . . 57.4 52.0 99.3 46.8 41.8 83.9 10.6 10.2 15.5 

1Less than 2,500 grams (5 pounds S ounces).


21,50C-2,499 grams (3 pcunds 4 ounce3 to 5 pounds 8 ounces).


%ssthan 1,500 grams (3pounds40unces).


41ncludes races other than white and black.


‘Includes births with educational attainment of mother not stated.


NOTE Excludss data for Cahfornia, Texas, and Washington, wfichtid notrequire repoting ofeducational attainment of mother. 

24 
Table4. Rates of bwMtihweighL byage, edu~tional aWinmen4and matial*Ws ofmother andra@of cMM:To@l ofrepoting areas, 1980and 1985 

All =Hix White Black 

Age, years of school completed, and marital status of mother 1980 1985 198G85 1980 1985 1980-85 1980 1985 1980-85 

Rate per Percent Rate per Percent Rate per Percent 

Age 1,000 live births change 1,000 live births change 1,000 live births change 

Under 15years . . . . . . . . . . . . . . . . . . . . . . . . . . 146.3 128.5 – 12.2 111.5 104.6 – 6.2 172.1 147.5 -14.3 

15-19 yeare . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.2 92.7 -1.6 77.2 76.4 –1.0 139.6 133.4 – 4.4 

15-17 years . . . . . . . . . . . . . . . . . . . . . . . . . . 105.2 102.2 – 2.9 86.8 63.7 -3.6 142.8 138.5 – 3.0 

16-19years . . . . . . . . . . . . . . . . . . . . . . . . . . 88.0 87.4 -0.7 72.4 72.8 0.6 137.1 129.7 – 5.4 

20-24years . . . . . . . . . . . . . . . . . . . . . . . . . . . 69.2 69.0 – 0.3 57.2 57.5 0.5 126.2 120.3 -4.7 

25-29years . . . . . . . . . . . . . . . . . . . . . . . . . . . 58.2 59.2 1.7 50.3 50.2 – 0.2 112.2 119.8 8.8 

30-34years . . . . . . . . . . . . . . . . . . . . . . . . . . . 58.9 60.5 2.7 51.2 52.1 1.8 111.3 123.8 11.2 

35-39years . . . . . . . . . . . . . . . . . . . . . . . . . . . 69.9 69.0 –1.3 61.5 60.3 – 2.0 117.1 126.8 8.3 

40yearsandover . . . . . . . . . . . . . . . . . . . . . . . . 83.4 83.7 0.4 74.0 73.9 -0.1 123.7 136.5 10.3 

Educational attainment 

0-6years . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . 93.6 93.1 -0.5 81.8 82.1 0.4 141.1 136.0 – 3.6 

%Ily ears . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100.7 101.4 0.7 82.7 83.9 1.5 146.5 145.6 -0.6 

12years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66.3 68.4 3.2 55.3 56.6 2.4 119.3 121.6 1.9 

13-15years . . . . . . . . . . . . . . . . . . . . . . . . . . . 55.5 55.9 0.7 46.2 46.4 0.4 106.6 106.1 – 0.5 

16yearsormore . . . . . . . . . . . . . . . . . . . . . . . . . 47.4 45.3 – 4.4 42.8 40.5 -5.4 90.4 94.9 5.0 

Marital status 

Married . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57.7 55.7 – 3.5 52.9 51.3 – 3.0 102.6 100.5 – 2.0 

Unmarried . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115.8 109.4 -5.5 90.5 86.0 – 5.0 143.0 139.9 -2.2 

‘Includes races other than white and black. 

2Excludes data for California, Texas, and Washington, which did not require reportingof educational attainment of mother. 

NOTE Low birth weight islessthan 2,500grams (5pounds Bounces). 

Table5. Rates oflow, mdemte~bw, andve~low M~hweigh~by ageofmother, fivetitih order, andm@of ctild:Untied S@teq 1985 

Lowbirthweight’ Moderately low birth weightz Very low birth weight= 

Age of mother and live-birth order Ail races4 White Black All races4 White Black All races4 White Black 

Rate perl,OOO1ive births 

Alleges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67.5 56.4 124.2 55.4 47.0 97.6 12.1 9.4 26.5 

Under20years5 . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.5 76.8 134.0 75.7 63.0 106.5 17.8 13.8 27.5 

Firstchild . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Secondchild . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Third child Andover . . . . . . . . . . . . . . . . . . . . . . . . 

20-24years5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Firstchild . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Secondchild . . . . . . . . . . . . . .. . . . . . . . . . . . . . . 

Third child Andover . . . . . . . . . . . . . . . . . . . . . . . . 

25-29years5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Firstchild . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

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

Third child Andover . . . . . . . . . . . . . . . . . . . . . . . . 

30-34yeare5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Firstchild . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

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

Thirdchild Andover . . . . . . . . . . . . . . . . . . . . . . . . 

35yearsandover5 . . . . . . . . . . . . . . . . . . . . . . . . . . 

Firstchild . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Secondchild . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Thirdchild Andover . . . . . . . . . . . . . . . . . . . . . . . . 

lLessthan 2,500 grams (5 pounds 80unces).


21,500-2,499 grams (3 pounds 4 ounces to 5 pounds 8 ounces).


3Less than 1,500 grams (3 pounds 4 ounces).


41ncludes races other than white and black,


51ncludes births with birth order not stated.


86.8 72.2 125.6 70.6 59.5 100.1 16.2 12.7 25.4 

110.3 90.8 149.1 89.1 74.0 118.7 21.3 16.7 30.3 

146.1 114.9 183.2 113.7 90.8 141.5 32.4 24.1 41.8 

69.0 57.5 120.3 56.9 48.1 95.3 12.1 9.3 25.0 

63.9 55.2 112.6 52.6 46.2 88.0 11.3 9.1 24.7 

63.8 53.2 111.7 52.9 44.9 89.2 10.8 8.3 22.6 

94.2 75.2 142.5 77.4 62.8 114.2 16.9 12.4 28.3 

59.2 50.2 119.8 48.8 42.1 93.3 10.4 8.0 26.5 

61.5 55.2 121.8 51.0 46.6 92.1 10.5 8.7 29.7 

49.6 42.0 105.7 40.8 35.1 82.0 8.8 6.9 23.7 

68.7 54.4 129.9 56.7 45.9 103.4 12.0 8.5 26.5 

60.5 52.1 123.8 49.5 43.3 95.4 11.0 8.8 28.5 

73.9 67.5 146.3 60.5 56.2 106.8 13.4 11.3 39.5 

51.3 44.6 113.3 41.8 36.9 86.8 9.5 7.7 26.5 

60.1 48.5 122.3 49.5 40.6 96.6 10.6 7.9 25.7 

70.7 61.9 128.1 57.8 51.1 100.3 12.9 10.8 27.8 

90.5 83.3 157.9 72.2 67.3 113.8 18.3 16.0 44.0 

63.0 56.0 121.4 51.0 45.9 92.7 12.0 10.1 28.7 

67.7 57.0 124.1 56.3 48.0 100.0 11.3 9.0 24.1 

25 
Appendixes 

Contents 

I. Source ofdataand sampling rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..27 

11. Definitions of terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..28 

IH. Completeness of reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29’ 

IV. Standardization for educational attainment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 

26 
Appendw I


Source of data and sampling


rates


Data for 1975–84 are based on 100 percent of the birth 

certificates fi,om States participating in the Vital Statistics 

Cooperative Program (VSCP) and on a 50-percent sample 

of births from all other States. In 1975, 23 States provided 

data through the VSCP (Colorado, Florida, Illinois, Iowa, 

Kansas, Louisiana, ,Maine, Maryland, Michigan, Missouri, 

Montana, Nebraska, New Hampshire, New York [exclusive 

of New York City], North Carolina, Oklahoma, Oregon, 

Rhode Island, South Carolina, Tennessee, Vermont, Virginia, 

and Wisconsin). By 1980, Alabama, Alaska, Arkansas, Connecticut, Hawaii, Idaho, Indkma, Kentucky, Massachusetts, 

Minnesota, Mississippi, Nevada, New Jersey, Ohio, Pennsylvania, South Dakota, Texas, Utah, Washington, West Virginia, Wyoming, and New York City were included in the 

VSCP, bringing the total to 44 States. 

For the years 1985–87, all States and the District of 

Columbia participated in the VSCP, and data ‘are based on 

100 percent of the birth certificates for all areas. 

A discussion of sampling procedures and sampling errors 

can be found in the Technical Appendix of Volume I of 

Vital Statistics of the United States for these years. 

Marital status—Nationai estimates of births to unmarried 

women for 1980 and 1985 are derived from MO sources. 

For 41 States and the District of Columbia, marital status 

was repo~ed directly on the birth certificate; for California, 

. . .. ,..,, ,.., ,,. . ,, .?! . . .:, 

Connecticut, Maryland, Michigan, Montana, Nevada; New 

York, Ohio, and Texas, m+tal ,s@ws was, @ferred from a 

comp&ison of the child’s andparent’s surnames. An evaluation 

of this method has been published (22). ~‘ ‘ ~ ~ 

Educational attainment of mother-~oy the ,years 1980-

85, educational attainment of the mother was reported on 

the birth certificates of 47 ‘States and the District of Columbia. 

The birth certificates of California, Texas, and Washington 

lacked this item. 

Period of gestation—In 1981, the birth certificates of 

49 States and the District of Columbia included a question 

on the date of the last normal menstrual period (LMP), the 

basis for the computation of the period of gestation. New 

Mexico’s birth cei-tificate lacked this item. In 1985, all States 

and the District of Columbia included a question on date 

of LMP. 

Interval since last live birth—In 1985, the birth certificates 

of 49 States and the District of Columbia included a question 

on the date of last live birth, the basis for computing the 

interval since the last live birth. The birth certificate of Texas 

did not include this item. 

All other variables discussed in this report were included 

on the birth certificates of all States and the District of 

Columbia. 

27 
Appendw II 

Definitionsof terms 

Race of chifd—Births are classified according to the race 

or national origin of the parents. When the parents are of 

different races and one parent is white, the child is assigned 

the other parent’s race. When the parents are of different 

races and neither parent is white, the child is assigned the 

father’s race—with one exception: If the mother is Hawaiian 

or part Hawaiian, the child is considered Hawaiian. When 

the race of one parent is missing on the birth certificate, 

the child is assigned the race of the other parent. When race 

is not reported for either parent, the child is assigned the 

race of the child on the immediately preceding record. 

The category “white” comprises births reported as white 

and births where race is reported as Hispanic. Because the 

races of the mother and child are identical for most births, 

for ease and clarity in writing, the race of the child is also 

used as the mother’s racial designation. 

Birth weight—The equivalents of the gram intervals in 

pounds and ounces are as follows: 

Less than 500 grams = 1 lb 1 oz or less 

500-999 grams = I lb 2 OZ–2 lb 3 oz 

1,000-1,499 grams = 2 lb 4 OZ–3 lb 4 oz 

1,500-I ,999 grams = 3 lb 5 OZ-4 lb 6 oz 

2,000-2,499 grams = 4 lb 7 OZ–5 lb 8 oz 

2,500-2,999 grams = 5 lb 9 OZ-6 lb 9 oz 

3,000-3,499 grams = 6 lb 10 02–7 lb 11 oz 

3,500-3,999 grams = 7 lb 12 OZ–8 lb 13 oz 

4,000-4,499 grams = 8 lb 14 OZ–9 lb 14 oz 

4,500-4,999 grams = 9 lb 15 OZ–I 1 lb Ooz 

5,000 grams or more = 11 lb 1 oz or more 

Birth weights of less than 2,500 grams are considered 

to be low birth weight; 1,500-2,499 grams, moderately low 

birth weight; and less than 1,500 grams, very low birth weight. 

Infants for whom birth weight was not reported are excluded 

from the computation of rates and percents. 

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 because it can be more accurately 

determined than the date of conception, which usually occurs 

about 2 weeks after the LMP date. Births occurring prior 

to 37 weeks of gestation are considered to be preterm or 

premature for purposes of classification. Births occurring at 

37 weeks of gestation or longer are referred to in this report 

as “full-term” births. 

Interval since last live birth—Data on the interval since 

the last live birth are derived from the date of birth and 

the date of the last live birth. An interval of zero months 

since the last live birth indicates the second born of a set 

of twins, the second or third born of a set of triplets, and 

so forth. Births with an interval of zero months are excluded 

from the interval category “less than 12 months.” 

28 
Appendw Ill


Completeness of reporting


In the period 1975–87, information on birth weight was 

missing from less than 1 percent of all birth certificates. 

Beginning in 1981, weeks of gestation have been imputed 

for records missing the day of last normal menstrual period 

(LMP) when there is a valid month and year- Each such 

record is assigned the gestational period in weeks of the preceding record that has a complete LMP date and the same computed months of gestation and 500 gram birth weight interval. 

A more complete dkcussion of this procedure and its implications is presented in a previous report (4). After imputation 

of gestational age for records missing the day of LMP, 3.8 

percent of the birth records in the reporting area in 1981 

and 3.9 percent in 1985 did not contain sut%cient information 

to assign weeks of gestation. 

The percent of records with missing information for age, 

educational attainment, and marital status of motheq live birth 

order and month of pregnancy prenatal care began was less 

than 3 percent for the data years shown. Information for 

the computation of interval since last live birth was missing 

fi-om 5 percent of the records for 1985. 

29 
.	 Standardmtion for educational 

attainment 

To eliminate the effects of differences in educational attainment when assessing the risk of low birth weight, moderately low birth weight, or very low birth weight according 

to month prenatal care began, the direct method of standardization was used. The distribution of births for each race by 

the educational attainment of mothers who started prenatal 

care in the first or second month of pregnancy was used 

as the standard population. Standardization was performed 

separately for white and black births using the following 

formula 

mepe 

m,=— x 100 

P 

where 

ml = standardized percent low birth weight for given 

month prenatal care began 

m= = percent low birth weight for each educational attainment group for given month care began 

p= =	 number of births for each educational attainment 

group for mothers starting care in the first or 

second month of pregnancy 

P =	 total number of births to mothers starting care 

in first or second month of pregnancy 

30 
.Vital and Health Statistics 

series descriptions ‘ 

SERIES 1.	 Programs and Collection Procedures—Reports describing 

the general programs of the National Center for Health 

Statistics and its offices and divisions and the data collection methods used. They also include definitions and 

other material necessary for understanding the data. 

SERIES 2.	 Data Evaluation and Methods Research—Studies of new 

statistical methodology including experimental tests of 

new suwey methods, studies of vital statistics collection 

methods, naw analytical techniques, objective evaluations 

of reliability of collected data, and contributions to 

statistical theory. Studjes also include comparison of 

U.S. methodology with those of other countries. 

SERIES 3.	 Analytical and Epidemiological Studies—Reports presenting analytical or interpretive studies based on vital 

and health statistics, carrying the analysis further than 

the expository types of reports in the other series. 

SERIES 4.	 Documents and Committee Repotts-Final reports of 

major committees concerned with vital and health statistics and documents such as recommended model vital 

registration laws and revised birth and death certificates. 

SERIES 5.	 Comparative International Vital and Health Statistics 

Reports-Analytical and descriptive reports comparing 

U.S. vital and health statistics with those of other countries. 

SERIES 6.	 Cognition and Suwey Measurement—Reports from the 

National Laboratory for Collaborative Research in Cognition and Survey Measurement using methods of cognitive 

science to design, evaluate, and test survey instruments. 

SERIES 10.	 Data From the National Health Interview Survey-Statistics on illness, accidental injuries, disability, use of hospital, medical, dental, and other services, and other 

health-related topics, all based on data collected in the 

continuing national household intemiew survey. 

SERIES 11. Data From the National Health Examination Survey and 

the National Health and Nutrition Examination Survey— 

Data from direct examination, testing, and measurement 

of national samples of the civilian noninstitutiona lized 

population provide the basis for (1) estimates of the 

medically 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. 

SERIES 12.	 Data From the Institutionalized Population Sutveys-Discontinued in 1975. Reporta from these surveys are included in Series 13. 

SERIES 13.	 Data on Health Resources Utilization—Statistics on the 

utilization of health manpower and facilities providing 

long-term care, ambulatory care, hospital 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 15.	 Data From Special Surveys-Statistics on health and 

health-related topics collected in special surveys that 

are not a part of the continuing data systems of the 

National Center for Health Statistics. 

SERIES 16.	 Compilations of Advance Data From Vital and Health 

Statistics—These reports provide early release of data 

from the National Center for Health Statistics’ health and 

demographic surveys. Many of these releases are followed 

by detailed reports in the Vital and Health Statistics 

Series. 

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 time series analyses; 

and statistics on characteristics of deaths not available 

from the vital records based on sample surveys of those 

records. 

SERIES 21.	 Data on Natality, Marriage, 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 analyses; studies of fertili~ 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 Mortality and Natality Surveys— 

Discontinued in 1975. Reports from these sample surveys 

based on vital records are included in Series 20 and 21, 

respectively. 

SERIES 23.	 Data From the National Survey of Family Growth— 

Statistics on fertility, family formation and dissolution, 

family planning, and related maternal and infam health 

topics derived from a periodic survey of a nationwide 

probability sample of women 15-44 years of age. 

SERIES 24. Compilations of Data on Natality, Motiality, Marriage, 

Divorce, and Induced Terminations of Pregnancy—Advance reports of births, deaths, marriages, and divorces 

are based on final data from the National Vital Statistics 

System and are published annually as supplements to the 

Monthly Vital Statistics Report (MVSR). These reports are 

followed by the publication of detailed data in Vital Statistics cf the United States annual volumes. Other reports 

including induced terminations of pregnancy issued periodically as supplements to the MVSR provide selected findings based on data from the National Vital Statistics 

System and may be followed by detailed reports in Vital 

and Health Statistics Series. 

For answers to questions about this report or for a list of titlea of 

reports published in these series, contact 

Scientific and Technical Information Branch


National Center for Health Statistics


Centers for Disease Control


Public Health Service


Hyattsville, Md. 20782


301 –436-8500