Vital and

Health Statistics

Health and

Demographic

Characteristics of

Twin Births: United

States, 1988

Series 21:

Data on Natality, Marriage, and Divorce

No, 50

National trends in twin birth incidence by race of child are analyzed for the

period 1950-88, Also reviewed are maternal and infant health and

demographic characteristics associated with twin delivey for the year 1988,

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Public Health Service

Centers for Disease Control

National Center for Health Statistics

Hyattsville, Matyland

June 1992

DHHS Publication No. [PHS) 92-1928
Copyright Information

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

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

appreciated.

Suggestad Citation

Taffel SM. Health and demographic characteristics of twin births: United States,

1988. National Center for Health Statistics. Vital Health Stat 21 (50). 1992.

Llbrsry of Congress Cataloging-in-Publication Data

Taffel, Selma.

Health and demographic characteristics of twin births ; Unted States,

1988.

p. cm. – (Vital and health statistics. Series 21, Data on natality,

marriaga, and divorce : no. 50) (DHHS publication : no. (PHS) 92–1772)

Author: Selma M. Taffel,

“National trends in twin birth incidence by race of child are analyzed for

the period 1950–88. Also reviewed are maternal and infant health and

demographic characteristics associated with twin delivery for the year f 988.”

Includes bibliographical references.

ISBN 0-8406-0463-7

1. Twins– United States –Statistics. 2. Multiple birth – United

States – Statistics, 3, United States – Statistics, Medical. 1,National Center for

Health Statistics (U.S.) Il. Title, Ill. Series. IV. Series: Vital and health statistics,

Series 21, Data from the National Vital Statistics System : no, 50.

[DNLM: 1. Birth Rate –trends – United States– statistics. 2, Maternal

Age– United States– statistics. 3. Pregnancy, Multiple– United

States – statistics, 4. Twins – United States – statistics,

W2 A N146vu no, 50]

HA21 1.A3 no. 50

[RG696.U6]

304.6’3’0973021 s–dc20

[304.6’3]

DNLM/DLC 92-19065

for LibraW of Congress CIP
National Center for Health Statistics

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

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

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

Robert A. Israel, Associate Director for International

Statistics

Stephen E. Nieberding, Associate Direclor for

Management

Charles J. Rothwell, Associate Director for Data

Processing and Services

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

and Methodology

David L. Larson, Assistant Director, Atlanta

Division of Vital Statistics

John E. Patterson, Director

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

Robert L. Heuser, M.A., Chiej Natali@, Mawiage and

Divorce Statistics Branch

Joseph D. Farrell, ChieJ Systems and Programming

Branch

Mabel G. Smith, Chie$ Statistical Resources Branch
Contents

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

Trends in twin birth incidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Age of mother and live-birth order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Sex ratio at birth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Period of gestation and birth weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Apgar score . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., .,.,,. . . . .

List of detailed tables . . . . . . .

Appendix

Technical notes . . . . . . . . . . . . .

List of text figures

. . . .

. . . .

. . . . . . .

. . . . . . .

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

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

1. Twin birth ratios by race of child: United States, 1950-88 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 Percent distribution of twin and singleton live births by period of gestation, according to race of chiId:

United States, 1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Symbols

--- Data notavailable

Quantity zero

0.0 Quantity more than zero but less than

0.05

1

2

3

4

5

7

8

9

10

17

2

5

* Figure does not meet standard of

reliability or precision

...

Ill
Health and Demographic

Characteristics of Twin

Births: United States, 1988

by Selma M. Taffel,

Division of Vital Statistics

Introduction

Information on the plurality of births derived from process was discontinued, and it was no longer possible to

live birth certificates has been published annually in the determine the number and composition of plural sets.

United States since 1917. Before 1959, the live birth and Because of the lack of such information for recent years,

fetal death records for sets of multiple births were matched. information presented in this report refers only to the

Beginning with the 1959 data year, however, this matching number of twin live births.

1
Trends in twin birth

incidence

Both the number of twin live births and the ratio of

twin births per 1,000 total live births have risen fairly

steadily since the early 1970’s (table 1 and figure 1). This

rise follows a slight decline in twin birth ratios from 1950

to the late 1960’s. By 1988, there were 21.8 twin live births

per 1,000 total live births in the United States, an increase

of 22 percent over the twinning ratio of 17.8 in 1971. The

1988 ratio is the highest ratio observed in the last four

decades. A rising proportion of twin births since the 1970’s

has also been noted in England and Wales (l).

The recent rise in twinning incidence reflects a change

in the age distribution of women at childbirth, with more

women giving birth at older ages (see “Age of mother and

live-birth order”), and an increased use of fertility drugs,

which greatly increases the risk of multiple ovulation and

subsequent delive~ of multiple births (2). In 1988, approximately 1.9 million women, ages 15–44, reported that they

had ever used ovulation-inducing drugs. This figure is up

from 1.1 million in 1982 (unpublished tabulations from the

1982 and 1988 National Surveys of Fami[y Growth, National Center for Health Statistics).

During all years for which data are available, the

twinning ratio for black births exceeds the ratio for white

births. In 198S, the ratio of 25.4 for black births was

19 percent higher than the ratio of 21.4 for white births.

The racial differential has narrowed considerably since

1971, when the black ratio exceeded the white ratio by

32 percent (table 1). The narrowing of the racial differential is due to the more rapid increase in twinning

incidence for white births than for black births (26 percent and 13 percent, respectively).

30 -

29 —

28 —

27 —

26

25

24 —

o

: 23

-’

; 22

0.

z 21

2

20

19

18 —

17

16

15

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4’

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●* ●*

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Black

Races other than

white

All races

White

01 I I I I I

1950 1960 1970 1980 1990

SOURCE, Nat!onal Center for Health Statlst!cs, National Vttal Statmtlcs System, 1950-88

NOTES: Data not ava!labla for black births for 1959-70 and for other racial groups for 1969-70,

RatLos are live btrths in twin deliveries per 1,000 total I!ve births,

Figure 1. Twin birth ratios by race of child: United States, 1950-88

2
Age of mother and

live-birth order

The incidence of twinning increases with the mother’s

age, up to ages 35–39 years, and then declines. This

pattern is evident for both white and black births (table 2).

It has been attributed to the rise in the level of gonadotropin with age, with maximum stimulation of follicles

occurring at ages 35–39, and a subsequent decline in

ovarian function at older ages (2).

Since the mid-1970’s, the proportion of births to

\l,omen in their thirties has risen steadily. In 1988, 20.6 percent of all births were to women 30–34 years of age,

81 percent more than the comparable proportion in 1971

(11.4 percent). Similarly, in 19SS, 6.9 percent of births

were to women 35–39 years of age, 50 percent more than

the 4.6 percent in 1971.

These increases are a major reason for the recent rise

in the twinning ratio. From 1971 to 1988, 39 percent of

the increase in twinning incidence for white births and

50 percent of the increase for black births can be attributed to the change in the age distribution of women giving

birth during this period. If the age distribution of mothers

in 198S were exactly the same as in 1971, the 19S8 overall

and black hvinning ratios would have been 6 percent

lower, and the 19SS white twinning ratio would have been

S percent lower (table 3).

An independent effect of parity of equal or greater

importance than that of maternal age has been obsemed

in a number of previous studies (3-5). However, it is not

possible to determine the exact influence of parity from

data derived from birth certificates, because each liveborn twin in a twin delivery is assigned a different,

adjacent, live-birth order. Thus, if a mother had one

previous live-born child, the first born of a set of twins

would be assigned live-birth order tXJOwhile the second

would be assigned live-birth order three. However, despite

this shortcoming, it is evident that there is a greatly

increased incidence of twinning for high-order compared

with low-order births.

As indicated in table 4, the twinning ratios for fourth,

fifth, and higher birth orders are about four times as high

as the ratio for first-order births. These differences are not

due to the older ages of women having high-order births.

For all maternal ages and for both white and black births,

twinning ratios increase with birth order and are substantially higher for high- than for low-birth orders. Previous

studies indicate that maternal age and birth order effects

on twinning incidence are most pronounced for dizygotic

(fraternal) twins, with little or no difference for monozygotic (identical) twin deliveries (3,4,6).

Twin birth ratios for American Indian, Chinese, Japanese, Filipino, and other Asian and Pacific Islander

births are 13 to 31 percent lower than for white births and

26 to 42 percent lower than for black births, despite a

generally higher proportion of births to older mothers and

lower incidence of teenage births for these racial groups.

These lower twin ratios reflect a much reduced twinning

ratio for almost all age groups (table 5). The age groups

analyzed are 10-year intervaIs because of the small number of twins for some racial groups.

Variation in twinning incidence among racial and

ethnic groups is due primarily to differences in dizygotic

twinning rates. It has been observed that the rate of

monozygotic hvinning is fairly constant throughout the

world. Several factors have been identified to explain

racial differences in dizygotic twinning incidence. Among

these are genetic disposition, which is inherited primarily

through the mother, and undernourishment, which decreases gonadotropin secretion and hence incidence of

multiple delivery (2).
Sex ratio at birth

There is a distinct difference in the sex ratio at birth 4.5 percent higher than the ratio of 1,006 for twin births.

(the number of male births per 1,000 female births) for As indicated in table 6, the ratio is higher for singleton

twin and singleton live births. The sex ratio for twin births births for all maternal ages, except 40-44 years of age,

by ageofmother tends tovaryfrom year to year because where it is the same. This general pattern is evident for

of small numbers. Therefore, data analyzed in this report both white and black births, but the sex differential by

are for the combined 3-year period 1986-88. During this plurality is less for black births.

time, the sex ratio for singleton live births was 1,051,
Period of gestation and

birth weight

The gestationaI age of a newborn is determined from

the first day of the mother’s last normal menstrual period

and the date of birth. Short gestational periods are far

more common for twins than for singletons (table 7 and

figure 2). In 1988, almost five times the proportion of

twins as of singletons were born preterm (before 37 weeks

gestation) (45.0 percent compared with 9.4 percent).

It has been suggested that the greater risk of preterm

delivery for twins is due to uterine overdistention, mechanical stretching of the cervix, and decreased uterine blood

death for multiple births (7) and is one of the major

causes of infant mortality for twins (8).

Black twin births are more Iikely to be born preterm than white twin births (53.4 percent compared

with 43.0 percent). However, the risk of preterm delivery for white twins compared with white singletons is

far greater than for black twins compared with black

singletons. Five and one-haIf times the proportion of

white twins as white singletons are born before 37

weeks compared with three times the proportion of

flow (2). Pre;erm birth is the leading cause of neonatal black twins-as black singletons.

50 r White births

births

h

E

~sor Black births

Less than 28-31 32-35 36 37-39 40 41 42 weeks

28 weeks weeks weeks weeks weeks weeks weeks and over

Period of gestation

SOURCE: National Center for Health Statistics, National Vital Statistics System, 1988

Figure 2, Percent distribution of twin and singleton live births by period of gestation, according to race of child: United States, 1988

5
Slightly more than one-half of twin babies are born at

term (37–41 weeks gestation) compared with about threequarters of singleton births. There are relatively few twins

born post-term (3.7 percent compared with 13.7 percent

of singletons), and racial differences are minor for postterm deliveries.

The average length of gestation for singletons is 39.3

weeks, about 3 weeks longer than the twin average of 36.2

weeks, Approximately the same differential is evident for

white and black births (table 7),

It is well known that twins weigh less at birth than

singletons. While their lower birth weight is due in part to

shorter gestational periods, there are major differences in

birth weight for equal periods of gestation (table 8). More

than twice the proportion of twins than singletons born

before 37 weeks gestation weigh less than 2,500 grams

(75,5 percent compared with 34.6 percent). Similarly, more

than twice the proportion of premature twins than premature singletons weigh less than 1,500 grams (19.5 percent

compared with 9.3 percent). Less than 1 percent of twins

born preterm weigh 3,500 grams or more compared with

14.0 percent of singletons,

At 37–39 weeks of gestation, the disparity in birth

weight between twins and singletons is even more pronounced, with 28.8 percent of twins weighing less than

2,500 grams compared with only 4,1 percent of singletons.

While 34.4 percent of singletons with these gestations

weigh at least 3,500 grams, only 4,3 percent of twins attain

this birth weight,

For gestations of 40 weeks and over, the proportion of

low-birth-weight infants (Iess than 2,500 grams) declines

to 26.5 percent for twins, The disparity with singleton

birth weight becomes even more evident, with only 1,6 percent of singletons weighing this little,

For all periods of gestation, the risk of low birth

weight for both black twin and singleton births fa,r exceeds

that for white births, and this racial differential increases

as period of gestation lengthens. Thus, while only 11 percent more black twin preterm than white twin preterm

births were low birth weight (81,4 percent compared with

73.6 percent), this racial difference increases to 58 percent for gestations of 40 weeks and over (37.5 percent

compared with 23,7 percent).

The fact that twins have on the average far lc~werbirth

weights than singletons of matched gestational ages suggests that other factors are responsible for their reduced

birth weight. Several explanations have been offered:

. The overcrowding in the uterus limits the area

available for placentaI growth, leading to placental

insufficiency.

. The inability of the mother to provide adequate nourishment to support optimal growth of two fetuses,

. The blood supply to the uterus is not sufficient to

support the same rate of growth for a multiple as for a

single pregnancy (9).
Apgar score

The Apgar score, developed by Virginia Apgar in

1952, is used to evaluate the physical condition of an

infant at 1 and 5 minutes after birth. The score may be

predictive of an infant’s chance for survival and often is

used as an indication of whether immediate medical

attention is required. The score is the sum of five signs of

the physical condition of the infant, each having a value of

O, 1, or 2. These are heart rate, respiratory effort, muscle

tone, reflex irritability, and color. A score of O-3 indicates

that the infant is severely depressed; 4-6, moderately

depressed; and 7–10, that the infant is in good to excellent

condition. The l-minute score reflects the infant’s condition at birth, while the 5-minute score is a better predictor

of long-term health and survival.

As indicated in table 9, more than one-fifth of twins

(21.4 percent) had a l-minute score of less than 7; a score

this low was more common for black twins than for white

twins (28.0 percent compared with 19.6 percent). A low

l-minute score was 2% times as frequent for twins as for

singletons, regardless of race. White singletons were 46 percent more likely than white twins to have optimal l-minute

scores of 9 or 10 (42.1 percent compared with 28.8 percent), but this differential increased to 74 percent for

black births (43.9 percent compared with 25.3 percent).

While 5-minute scores are considerably higher than

l-minute scores for both twins and singletons, the differential by plurality is still quite marked. A Win is more

than four times as likely as a singleton to have a 5-minute

score of Iess than 7 (6.5 percent compared with 1.5 percent). About 7 out of 10 twins, compared with about 9 out

of 10 singletons, had high 5-minute scores of 9 or 10.

Again, large differentials in 5-minute Apgar scores by

plurality are evident for both races.

Weight at birth is highIy correlated with Apgar scores.

At 1 minute after birth, low-birth-weight babies are about

nine times as likely as those of higher weights to be

classified as severely depressed (scores of O to 3) and

about three times as likely to be classified as moderately

depressed (scores of 4 to 6).

Differentials for 5-minute Apgar scores for low-birthweight infants are even larger. As noted earlier, the birth

weight of twins is less favorable than that of singletons.

About 50 percent of twins weigh less than 2,500 grams at

birth compared with 6 percent of singletons. Thus, the

higher prevalence of low birth weight among twin births is

one of the major reasons for the relatively large proportion of low 1- and 5-minute scores.

An additional reason is that a very high proportion of

twins are delivered by cesarean section. In 1988, aImost

two-thirds of twin deliveries compared with about onequarter of singleton deliveries were by cesarean section

(unpublished data from the National Hospital Discharge

Survey of the National Center for HeaIth Statistics). Both

1- and 5-minute Apgar scores are Iower for cesarean than

for vaginal deliveries (unpublished data from the 1980

National Natality Survey of the National Center for Health

Statistics).
Discussion

It is evident that the health status at birth is far more

precarious for twins than for singletons. A study of congenital anomalies and birth injuries among live births

found that the overall incidence of congenital defects was

1S percent higher among births in plural than in single

deliveries, and that for almost all anomalies examined

there was a higher incidence for plural births. Additionally, there was a far greater likelihood of brain, bone, or

nerve injury at birth for a multiple than for a single birth

(10). The lower birth weight and higher incidence of

prematurity for twin births have been identified as critical

factors in their higher rates of infant mortality (8).

With the continuing increase in the number of twin

births in the United States, research into the prevention of

preterm delivery and low birth weight for multiple births is

of increasing importance. This will be aided by the wealth

of new information that will become available from the

revised U.S. Standard Certificate of Live Birth, implemented by all but three States in 19S9.

Included on the new certificate are a number of

questions particularly relevant to the study of twin health,

These include medical risk factors of pregnancy, such as

anemia, pregnancy-associated hypertension, and eclampsia; and complications of labor and delivery, such as fetal

distress and dysfunctional labor.

In addition, information will be collected on lifestyle

factors – tobacco and alcohol use and weight gain during

pregnancy– as well as method of delivery and abnormal

conditions and congenital anomalies of the newborn. For

some of these risk factors and conditions, there will be

only a relatively small number of events annually. Thus, it

may be necessary to combine several years of data for

meaningful analyses.

This new information, combined with other socioeconomic and health data available from birth certificates,

will provide a more complete and clearer picture of the

risks of multiple delivery than is presently obtainable from

periodic sampIe surveys.
References

1. Betting BJ, MacDonald Davies I, and h4acFarlane AJ.

Recent trends in the incidence of multiple births and

associated mortality. Archives of Disease in Childhood

62:941-50. 19S7.

2. Danforth DN. Danforth's obstetrics andg/necolog. 6thed.

Philadelphia: J.B. Lippincott CO. 1990.

3. Gittelsohn AM, Milham S Jr. Observations on twinning in

NewYorkS tate.BrJ PrevSocilled 19(1):S-17. 1965.

4. Heuser RL. Multiple births, United States–1964. National

Center for Health Statistics. Vital Health Stat:21(14). 1967.

5. Williams JW. Williams obstetrics. 15th ed. New York:

Appleton-Century-Crofts. 1976.

6. Yerushalmy J, Sheerar SE. Studies ont\vins. I. The relation

of order of birth and age of parents to the frequency of

like-sexed and unlike-sexed twin deliveries. Hum Bio

12(1):95-1 13.1940.

7. American ColIege of Obstetricians and Gynecologists.

Multiple gestation. ACOGTechnical Bulletin Number 131.

Washington, DC. 19S9.

8. Kfeinman JC, Fowler MG, and Kessel SS. Comparison of

infant mortality among twins and singletons: United States

1960 and 19S3. Am J Epidem 133(2):13343. 1991.

9. Bulmer MG. The biology of twinning in man. Oxford:

Clarendon Press. 1970.

10. Taffel SM. Congenital anomalies and birth injuries among

live births: United States, 1973-74. National Center for

Health Statistics. Vital Health Stat:21(31). 197S.
List of detailed tables

1. Twin birth ratios by race of child: United States,

1950-88 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2. Twin birth ratios by age of mother and race of child:

United States, 1988 . . . . . . . . . . . . . . . . . . . . . . . . . . .

3. Observed and adjusted twin birth ratios by race of

child: United States, selected years, 1971-88 . . . . . . .

4. Twin birth ratios by live-birth order, age of mother,

and race of child: United States, 1988 . . . . . . . . . . . .

5. Twin birth ratios byspecified race ofchildand age of

mother: United States, 1988.. . . . . . . . . . . . . . . . . . .

6. Sex ratio of twin and singleton live births by age of

mother and race of child: United States, 1986-88

average . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7. Percent distribution of Winandsingleton live birtklsby

10 period of gestation and race of child: United St;~tes,

1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

11 8. Percent distribution oftwinand singleton live birtk)sby

birth weight, according to period of gestation and race

11 of child: United States, 1988.. . . . . . . . . . . . . . . . . . . 14

9. Percent distribution of Winandsingleton live birtk~sby

12 1- and 5-minute Apgar scores, according to race of

child: Total of 46 reporting States and the District of

Columbia, 1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

12

13

10
Table 1. Twin birth ratios by race of child: United States, 1950-88

(Ratios are live births in twin deliveries per 1,000 total live births)

All other

All races White Total Black

Number Number

of twin

Number Number

Total of twm Total of twin Total of twin

Year

Total

births births Ratio births births Ratio births births Ratio births births Ratio

1988 .,.......

1987, ,, . . . . . .

1986 . . . . . . . . .

1985 . . . . . . . . .

19841 . . . . . . . . .

19831 . . . . . . . . .

19821 . . . . . . . . .

19611 .,.......

19801 .,.......

19791 ..!......

19781 . . . . . . . . .

19771, . . . . . . . .

19761 . . . . . . . . .

19751 . . . . . . . . .

19741 . . . . . . . . .

19731 . . . . . . . . .

19721 . . . . . . . . .

19712 . . . . . . . . .

19702 . . . . . . . . .

19692 . . . . . . . . .

19662 . . . . . . . . .

19673 . . . . . . . . .

19682 . . . . . . . . .

19652 . . . . . . . . .

19642 . . . . . . . . .

19632,4, . . . . . . .

196224. . . . . . . .

19612 . . . . . . . . .

19602 . . . . . . . . .

19592 . . . . . . . . .

19582 .,,,.....

19572 . . . . . . . . .

19562 . . . . . . . . .

1955 . . . . . . . . .

19542 . . . . . . . . .

19532 . . . . . . . . .

19522 . . . . . . . . .

19512 .,.......

1950 . . . . . . . . .

65,315

61,778

79,485

77,102

72,949

72,287

71,631

70,049

68,339

66,856

64,163

62,680

60,664

59,192

57,636

56,777

59,122

63,298

. . .

. . .

69,300

68,336

70,340

74,594

78,954

80,044

80,180

84,926

65,440

86,426

84,934

85,196

64,765

84,394

82,626

61,000

78,457

75,335

73,499

3,909,510

3,809,394

3,756,547

3,760,561

3,669,141

3,638,933

3,680,537

3,629,238

3,612,258

3,494,398

3,333,279

3,326,632

3,167,768

3,144,198

3,159,958

3,136,965

3,258,411

3,555,970

3,731,388

3,600,206

3,501,564

3,520,959

3,606,274

3,760,358

4,027,490

4,098,020

4,167,362

4,268,326

4,257,850

4,244,796

4,203,612

4,254,784

4,163,090

4,047,295

4,017,362

3,902,120

3,846,986

3,750,850

3,554,149

21.8

21.5

21.2

20.5

19.9

19.9

19.5

19.3

18.9

19.1

19.2

18.9

19.2

18.8

18.3

18.1

18.1

17,8

. . .

. . .

19.8

19.4

19.5

19.8

19.6

19.5

19.2

19.9

20.1

20.4

20.2

20.0

20.4

20.9

20.6

20.8

20.4

20.1

20.7

65,136

62,952

61,385

59,420

56,439

55,766

55,229

53,653

52,397

51,372

49,461

48,824

47,521

46,266

45,573

44,452

46,302

49,576

. . .

---

55,464

54,123

55,430

58,436

62,076

61,062

61,792

67,442

68,414

69,230

68,314

68,788

68,724

69,079

67,705

66,518

65,232

62,772

61,233

3,046,162

2,992,468

2,970,439

2,991,373

2,923,502

2,904,250

2,942,054

2,908,669

2,898,732

2,808,420

2,681,116

2,691,070

2,567,614

2,551,996

2,575,792

2,551,030

2,655,556

2,919,746

3,091,264

2,993,614

2,912,224

2,922,502

2,993,230

3,123,860

3,369,160

3,326,344

3,394,068

3,600,864

3,600,744

3,597,430

3,572,306

3,621,456

3,545,350

3,458,448

3,443,630

3,356,772

3,322,658

3,237,072

3,063,627

21.4

21.0

20.7

19.9

19.3

19.2

18.8

18.4

18.1

18.3

18.4

18.1

18.5

18.1

17,7

17.4

17.4

17.0

---

---

19.0

18.5

16.5

16.7

18.4

18.4

18.2

18.7

19.0

19.2

19.1

19.0

19.4

20.0

19.7

19.8

19.6

19.4

20.0

20,179

18,826

18,100

17,662

16,510

16,521

16,402

16,396

15,942

15,486

14,702

14,056

13,143

12,926

12,263

12,325

12,820

13,722

---

---

13,836

14,213

14,910

16,158

16,878

16,356

15,788

17,484

17,026

17,196

16,620

16,408

16,041

15,315

14,921

14,482

13,225

12,563

12,266

863,348

816,906

786,108

769,188

745,639

734,683

738,483

720,569

713,526

685,978

652,163

635,562

600,174

592,202

584,166

585,935

602,853

636,224

640,122

606,592

589,340

598,457

613,044

636,498

658,330

638,928

641,580

667,462

657,106

647,366

631,506

633,328

617,740

588,847

573,732

545,348

524,326

513,778

490,522

23.4

23.0

23.0

23.0

22.1

22.5

22.2

22.8

22.3

22.6

22.5

22.1

21.9

21.8

21.0

21.0

21.3

21.6

---

. . .

23.5

23.7

24.3

25.4

25.6

25.6

24.6

26.2

25.9

26.6

26.3

25.9

26.0

26.0

26.0

26.6

25.2

24.5

25.0

17,052

16,042

15,252

15,137

14,111

14,142

14,042

14,340

14,026

13,782

13,116

12,512

11,786

11,674

11,041

11,201

11,670

12,656

.-.

. . .

. . .

---

---

. . .

. . .

.-.

. . .

---

---

---

15,992

15,773

15,466

14,806

14,477

13,998

12,617

12,155

11,794

671,976

641,567

621,221

608,193

592,745

586,027

592,641

567,797

589,616

577,855

551,540

544,221

514,479

511,581

507,162

512,597

531,329

564,960

572,362

543,132

531,152

543,976

558,244

581,126

607,558

580,658

584,610

611,072

602,264

605,962

594,500

596,050

584,572

558,251

544,288

517,576

497,860

489,282

466,718

‘ 25.4

25.0

24.6

24.9

23.8

24.1

23.7

24.4

23.8

23.9

23.8

23.0

22.9

22.8

21.8

21.9

22.0

22.4

---

. . .

. . .

---

..-

---

. . .

.-.

. . . .

. . .

---

.-.

26.9

26.5

26.5

26.5

26.6

27.0

25.7

24.8

25.3

1Based on 100 percent of births in selected 8tates and on a 50-percent sample of births in all other States see Technical notes.

2Based on a 50-percent sample Of births.

3Based on a 20. to 50-percent sample of birlhs.

4Figures by race exclude data for New Jersey.

11
Table 2. Twin birth ratios by age of mother and race of child: United States, 1988

(Ratios are live births in twin deliveries per 1,000 total live births in specified group)

Race of child

Age of mother A// racesl White Black

Alleges . . . . . . . . . 21,8 21,4 25,4

13.4

13.8

19.0

22.7

26.6

29.2

22.4

*

14.0

12.6

17.6

22.1

26.4

29.8

23.0

*

13,1

16,6

24.6

29,5

32.2

32.0

23,5

*

llncludes races other than white and black.

Table 3. Observed and adjusted twin birth ratios by race of child: United States, selected years, 1971-88

(Ratios are live births in twin deliveries per 1,000 total live births in specified group, Adjusted ratios reflect the age distribution of mothers in 1971

in specified racial group)

A// racesl White Black

Percent Percent Percent

Year Observed Adjusted differenc$ Observed Adjusted differenc# Observed Adjusted differenc$

1966, . . . . . . . . . . . . . . . . . . . 21.6 20.4 –6,4 21.4 19,7 –7.9 25.4 23.9 –5.9

1987, . . . . . . . 21.5 20.2 –6.0 21.0 19.6 –6.7 25.0 23.7 -5.2

1966 . ., . . . . . . . . . . . . . . . 21,2 20.0 -5.7 20.7 19,3 -6.8 24.6 23.3 –5.3

1965, .,... . . . . 20,5 19.5 –4.9 19.9 78.7 -6.0 24.9 23.5 –5.6

1984, . . . . . . . . . . . . . . . . . . . 19.9 19.0 –4,5 19.3 18.3 -5.2 23.8 22.7 –4.6

1963 . . . . . . . . . . . . . . . . . . . 19,9 19.1 –4.0 19.2 16.4 -4.2 24.1 23.1 4.1

1962.,. ,. 19,5 16.6 -3,6 18.8 16.1 -3.7 23.7 22.7 –4.2

1981 ., . . . . . . . . . . . . . . . . . 19.3 18.8 -2.6 18.4 17.9 -2.7 24.4 23.6 –3.3

1960, . . . . . . . . . . . . . . . . . . 18.9 18.5 –2,1 18.1 17,7 -2.2 23.8 23.2 -2.5

1975 . . . . . . . . . . . . . . . . . . . . 18,8 18.8 18.1 18,1 22.6 23.1 1.3

1973, . . . . . . . . . . . . . . . . . . . 18.1 18.1 17.4 17,4 21.9 22.2 1.4

1971, . . . . . . . . . . . . . . . . . 17.8 17.8 17.0 17.0 22.4 22.4

1Includes races other than white and black.

‘Adlustedhwn ratto compared wtth obsewed twm ratm.

12
Table 4. Twin bitihratios bylive-bitih order, ageofmother, andrace of child: United States, 1988

(Ratios are live births in twin deliveries per 1,000 total live births in specified group)

Live-birth order

Age of mother and

race of chi/d Total 1

5 and

2 3 4 over

All racesl

Alleges . . . . . . . . . . . . . . . . . . . . . 21.8 10.8 23.3 33.2

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

42.5

13.8

46.1

7.0 32.2 50.7

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

76.6

19.0

107.7

9.5 21.6 34.8

25–29 years . . . . . . . . . . . . . . . . .

45.5

22.7

58.2

11.9 22.4 32.9

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

43.2

26.6

50.4

15.8 23.2 31.6

35-49years . . . . . . . . . . . . . ,,,,

42.6

28.3

47.5

18,6 26,0 30.4 35.2 36.7

White

Alleges . . . . . . . . . . . . . . . . . . . . . 21.4 10.9 23.1 32.9

Under20years, . . . . . . . . . . . . . .

42.4

12.6

44.4

6.5 33.1 51.5 76,2

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

*

17.6 9.2 20.9 34.5 46.3

25-29years . . . . . . . . . . . . . . . . . 22.1

55.4

12.0 22.2 32.9 43.1

30-34years . . . . . . . . . . . . . ,.,. 26.4

49.4

16.2 23.4 31.7 43.2

35-49years . . . . . . . . . . . . . . . . . 28.9

46.4

19.7 27.1 31.3 35.7 36.5

Black

Alleges . . . . . . . . . . . . . . . . . . . . . 25.4 10.6 26.3 36.3

Under20years . . . . . . . . . . . . . . .

45.5

16.5

56.4

8.0 31.2 50.7 79.7

20-24years . . . . . . . . . . . . . ,.,. 24,6

118.8

11.6 25,0 36.9 45.3

25-29years . . . . . . . . . . . . . ,.,. 29.5

63.7

13.6 25.6 35.7

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

47.1

32.2

59,3

15.3 25.4 33.4 43.2

35-49years . . . . . . . . . . . . . ..,. 30.6

57.3

16.0 24.6 30.0 36.7 43.4

1Includes races other than white and black,

Table 5. Twin birth ratios byspecified race ofchild and age of mother: United States, 1988

(Ratios are live births in twin deliveries per 1,000 total live births in specified group)

Race of child

Asian or Pacific islander

All American

Age of mother racesl White Black Indian Total Chinese Japaneae Hawaiian Filipino Other

All eges . . . . . . . . . . . . . . . 21.8 21.4 25.4 18.7 15.6 14.9 17.7 15.5 14.7 15.6

Under20years . . . . . . . . . . . 13.6 12.6 16.5 12,4 13.2 * *

18.6

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

*

21.0 20.1 26.7

11.4

16.5 14.0 12.2 14.8

30-39years . . . . . . . . . . . . . 27,3

13,8

27.2

13.3

32.1

14.6

24.9 18.0 16.9 20.0 17.5

40-49years . . . . . . . . . . . . . 22.1 22.6

17.4

23.3 *

18.3

14.1 * * * * 16.2

1Includes other races not shown separately.

13
Table 6. Sexratio oftwin and singleton Iivebirthsby age of mother and race of child: United States, 1986–88 average

(Ratios are the number of male births per 1,000 female births in specified group)

A// racesl White Black

Tw/n Sing/eton Twin Singleton Twm Singleton

Age of mother births births births births births births

All ages... . 1,006 1,051 1,009 1,055 996 1,033

Under15 years. ,. 665 1,047 947 1,079 808 1,026

15-19 years . . . . . . . . . . . . . . 981 1,055 979 1,060 988 1,042

20–24 years . . 1,008 1,050 1,006 1,054 1,006 1,033

25-29years. .,.... ,. 1,020 1,051 1,029 1,053 995 1,030

30–34years . . . . . . . . . . 995 1,053 995 1,056 986 1,030

35–39years. . 1,004 1,050 998 1,053 1,017 1,015

4G44years. . ,. 1,044 1,044 1,102 1,045 975 1,023

45–49years. 750 1,060 *

1,024 *1,044

‘Includes race$other than white and black.

Table 7. Percent distribution oftwinand singleton live bitihsby period of gestation andrace of child: United States, 1988

A// racesl White Black

Twin Singleton Twin Sing/eton Twin Singleton

Period of gestation births births births births births births

Livebrths2 85,315 3,821,810 65,136 2,979,007 17,052 654,623

Percent distribution

Total. . .

Under28weeks, . .

28-31 weeks . . . . . .

32-35weeks

36weeks . . . . . . . . . . .

37–39 weeks

40weeks ..,..,,. . .

41 weeks.....,,.

42weeks Andover . . . . . . . . . .

Under37weeks . . . . . .

100.0

4.3

6.3

22.2

12.2

41.4

6.6

3.1

3,7

45.0

100.0

0.7

1.0

4.5

3.2

40,1

22,1

14.7

13.7

9,4

100.0

3.4

5.5

21.7

12.4

43.3

7.0

3.2

3.5

43.0

100.0

0.5

0.8

3.6

2.8

39.4

23.1

15.7

14,1

7,7

100.0

6.3

9.4

24.7

11.0

33.6

5.6

2.6

4.2

53.4

Weeks

100,0

1,8

2,4

8,3

4,8

41.8

17.7

10.6

12.3

17.4

Mean . . . . . . . 36,2 39.3 36.4 39.5 35.3 36.6

1Includes races other than white and black.

2,nc,ude~blflh$ ~lth Pe,,~d of ~e$~atl~”not Stated,~h,~h ere ex~l”ded fr~m the computation Of the PerCent distnbutmr.

14
Table 8. Percent distribution of Winandsingleton live bitihsby bitihweight, according toperiod ofgestation andrace of child: United

States, 1988

A// racesl White Black

Period of gestation Twin Sing/eton Twin Sing/eton Twin Singleton

and biilh weight births births births bkths births births

All gestations

Live births2,3 . . . . . . . . . . . . . . . .

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

Lessthan l, 000 grams . . . . . . . . .

1,000-1,499 grams . . . . . . . . . . . . .

1,500-1,999 grams . . . . . . . . . . . . . .

2,000-2,499 grams . . . . . . . . .

2,500-2,999 grams . . . . . . . . . . . . . .

3,000-3,499grams . . . . . . . . .

3,500–3,999 grams . . . . . . . . . .

4,000grams ormore . . . . . . . . . .

Lessthan 2,500 grams . . . . . . . . .

Under 37 weeks

Live births3 . . . . . . . . . . . . . . . . . . . .

Total, . . . . . . . . . . . . . . . . . . . . . . .

Lessthan l,OOOgrams .,..... . . . . .

1,000–l,499 grams . . . . . . . . . . . . . . .

1,500–l,999grams . . . . . . . . . . . . .

2,000–2,499 grams . . . . . . . . . . . . . . .

2,500–2,999grams . . . . . . . . . . . . . . .

3,000-3,499 grams . . . . . . . . . . . . . . .

3,500-3,999grams . . . . . . . . . . . . .

4,000 gramsormore .,..,. . . . . . . . .

Lessthan 2,500 grams . . . . . . . . . . . . .

37-39 weeks

Live births3 . . . . . . . . . . . . . . . . . . . .

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

Lessthan l,OOOgrams . . . . . . . . . . . . .

1,000-11499 grams,,,..,.. . .

1,500-1,999 grams . . . . . . . . . . . . . . .

2,000-2,499grams . . . . . . . . . . . . . . .

2,500–2,999grams .,,,., . . . . . . . .

3,000-3,499grams .,...... . . .

3,500-3,999 grams . . . . . . . . . . . . . . .

4,000 gramsormore, . . . . . . . . . . . . .

Lessthan 2,500grams . . . . . . . . . .

40 weeks and over

Live births3 . . . . . . . . . . . . . . ,,..,.

Total, . . . . . . . . . . . . . . . . . . . . . . .

Lessthan 1,000 grams, . . . . . . . . . . . .

1,000-l,499grams . . . . . . . . . . . . . . .

l,500–l,999grame . . . . . . . . . .

2,000-2,499 grams . . . . . . . . . . .

2,500–2,999 grams, ,, . . . . . . . . . . . .

3,000–3,499grams ..,.... . . . . . . . .

3,500–3,999grams ..,..... . . . . . . .

4,000 gramsormore, ..,,.. . . . . . . .

Lessthan2,500 grams, . . . . . . . . . . . .

85,315

100.0

4.6

5.3

12.3

26.0

31.5

15.2

2.7

0.3

50.2

36,531

100.0

9.0

10,5

21.6

34.4

19.8

4,2

0.4

0.1

75.5

33,658

100.0

0.1

0.6

4.3

23.8

43.2

23.7

3.9

0.4

28.8

11,059

100.0

0.4

1.0

4.6

20.6

37.8

27.7

7.1

0.9

26.5

3,821,810

100.0

0.5

0.5

1.1

3.6

15.7

37.1

30.1

11.3

5.9

344,244

100.0

4.6

4.7

6.1

17.3

26.8

24.5

11.0

3.0

34.6

1,465,993

100.0

0.0

0.1

0.4

3.6

19.5

42.0

26.9

7.6

4.1

1,849,405

100.0

0.0

0.0

0.2

1.4

10.3

35.7

36.5

15.9

1.6

Number

65,136 2,979,007

Percent distribution

100,0 100.0

3.6 0.4

4.6 0.4

11.2 0.8

27.6, 3.1

32.8 13.8

16.7 36.5

3!1 32.3

0.4 12.7

47.1 4.7

Number

26,777 219,515

Percent distribution

100.0 100.0

7.5 4.0

9.7 4.3

20.6 7.6

35.7 17.0

21.4 26.8

4.5 24.8

0.4 12.0

0.1 3.5

73.6 32.9

Number

26,948 1,127,803

Percent distribution

100.0 100.0

0.1 0.0

0.4 0.1

3.7 0.4

22.4 3.0

43.4 17.5

25.3 41.8

4.3 28.9

0.4 8.5

26.6 3.4

Number

0,542 1,514,227

Percent distribution

100.0 100.0

0.3 0.0

0.6 0.0

3.6 0.1

19.2 1.1

37.7 9.0

29.6 34.4

7.9 38.1

1.1 17.3

23.7 1.3

17,052

100.0

8.6

8.0

16.3

29.2

26.4

9.8

1.4

0.2

62.2

8,559

100.0

14.1

13.3

23.9

30.0

15.1

3.1

0.3

*

81.4

5,424

100.0

0.4

1.4

7.2

30.3

41.6

16.7

2.3

*

39.2

2,057

100.0

●

2.2

8.5

26.1

37.6

20.9

3.6

*

37.5

654,623

100.0

1.3

1.1

2.2

7.1

23.3

38.6

20.8

5.6

11.7

107,564

100.0

6.1

5.6

9.2

18.1

26.7

23,5

8.8

1.9

39.1

258,893

100.0

0.1

0.1

0.8

6.2

27.1

42.2

19,2

4.3

7.2

253,430

100.0

0.1

0.1

0.4

2.9

17.8

41.9

28.1

8.7

3.5

‘Includes races olherlhan white and black.

‘Includes births with period of gestahon not stated.

Slncludestjdhsw{th brthweightn ots tated, wh!chare excluded from thecomputatlOn Ofthe PerCent dlStrlbUtl0n.

15
Table 9. Percent distribution oftwin and singleton live bitihsby l-and 5-minute Apgarscorea, according toraceof child: Total of46

reporting States andthe District of Columbia, 1988

A// raced White Black

Twin Sing/efon Twin Sirrg/efon Twin Singleton

Apgar score births btrths births births births births

l-minute score Number

Live births2 . . . . . . 66,979 2,946,186 50,613 2,282,720 14,494 552,096

Percent distribution

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

04 . . . . . . . . . . . . . . . . . . . . . 7.6 2,1 6.3 1,s 12.0 3.5

4–6 ...,.... . . . 13.8 6.4 13.3 6.2 16.0 7.6

7–8 . . . . . . . . . . . . . . . . . . . 50.5 49,0 51.5 49,9 46.6 45.0

9-10, ..,,.....,..,.,.. 26.1 42.5 28.8 42.1 25.3 43.9

Lessthan 7, . . . . . . . . . . . . . . . . 21.4 8.6 19.6 6.0 28.0 11.1

5-minute score Number

Live birthsz .,........,.. 66,979 2,946,186 50,613 2,282,720 14,494 552,096

Percent distribution

Total. . . . . . . . . . . . 100.0 100.0 100.0 100.0 100.0 100.0

0-3 . . . . . . . . . . . . . . . . . . . . . 2.5 0.5 1.9 0.4 4,6 1.0

4–6 . . . . . . . . . . . . . . . . . . . 4.0 1.0 3.4 0.9 6,3 1.7

7-8 ..,.,,,....,...,,. ,,. ,. 21.1 9.2 20.9 9.0 22.3 10.2

9–10 . . . . . . . . . . . . . . . . . . . 72.3 69.3 73.8 89.8 66.8 87.1

Lessthan 7,,....,.,.,,,,. 6.5 1.5 5.4 1.2 10.9 2,7

1Includes races other than wh(te and black,

21ncludes births with Apgar score not stated, wh!ch are excluded from the computation of the percent distribution.

NOTE: Excludes data for Cal] fornla, Delaware, Oklahoma, and Texas, which did notreporl Apgarscores oniheblP.h certificate.

16
Appendix

Technical notes

Source of data

Data shown in this report for 19S8 are based on

100 percent of the birth certificates in all States and the

District of Columbia. The data are provided to the National Center for Health Statistics through the Vital Statistics Cooperative Program (VSCP). In 1984 and earlier

years, the VSCP included va@ing numbers of States,

which provided data on 100 percent of their birth certificates. Data for States not in the VSCP were based on a

50-percent sample of birth certificates filed in those States.

Information on sampling procedures and sampling errors

for 1984 and earlier years is provided in the annual report,

V7tal Statistics of the United States, Volume I, Natality.

Racial classification

Racial designation shown in this report is that of the

child. The child’s race is determined from the race or

national origin of the parents. When only one parent is

white, the child is assigned the other parent’s race or

national origin. When neither parent is white, the child is

assigned the father’s race or national origin, with one

exception; if the mother is Hawaiian or part-Hawaiian, the

child is considered Hawaiian. If information on race is

missing for either parent, the child is assigned the known

race. When the information is missing for both parents,

the race of the child is as: igned according to the race of

the child on the previous record.

Computation of percents, medians, and

ratios

Percent distributions, means, and ratios are computed

using only events for which the characteristic is reported.

The number of births with information not stated is

subtracted from the total before computation of these

measures. An asterisk is shown in place of any derived

statistic based on fewer than 20 births in the numerator or

denominator.

17
New Electronic Data

Product Releases w

CK National Center for Health Statistics

CENTERS FOR DISEASE CONiiiOL

1988 National Maternal, and Infant Health Survey

The first public use tape for the National Maternal and

Infant Health Survey (NMIHS) that links vital records to

questionnaire responses given by mothers was released by

the National Center for Health Statistics (NCHS).

The NMIHS is designed to collect data on factors prior to

birth that could be related to adverse outcomes such as

low birth weight, stillbirth, infant illness, and infant death.

This survey is the first national survey to combine information from three sources, hospitak, prenatal health care

providers, and mothers, as a means of studying factors

related to pregnancy outcome. A second tape containing

data obtained from the hospitals’ and prenatal care providers’ questionnaires will be released in late 1992.

The first NMIHS file contains data from a sample ofi

c 9,953 women who had live births

. 3,309 women who had late fetal deaths

. 5,335 women who had infant deaths

These samples, once weighted, are designed to produce

national estimates.

Analysts who obtain the public use data tape are added

to the mailing list of the NCHS “1988 NMIHS Analysts

Group.” The group’s objective is to promote collaboration, avoid duplication of effort, and receive technical

notes and updates.

To obtain copies of this tape, please complete the order form below as well as the data users agreement on

the back of this release.

.—— ————— ———— ———— ____ ___!

To order from the National Technical Information Service

Please send _ copies of the 1988 NatkxM/ Matema/ and h?fant Health Survey Public-Use Data Tape

Tape characteristics Send check to:

Label: Standard label

Tracks: 9

Density: 6250 BPI

Record Length: 6436

Block Size: 32180

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

(703) 487-4650

Number of Records: 9,953 Live births

3,309 Fetal deaths

5,332 Infant deaths

Select one: Reel (2 reels) or Cartridge (1 cartridge)

Price: $590 Accession Number PB92-500081

Optional: Additional set of Documentation

Price: $26 Accession Number PB92-101 906
DATA USE AGREEMENT-The Public Health Service Act (42 U.S.C. 242m(d)) provides that the data collected by

the National Center for Health Statistics (NCHS) may be used only for the purpose for which they were obtained; any

effort to determine the identity of any reported cases, or to use the information for any purpose other than for health

statistical reporting and analysis, would violate this statutory restriction and the conditions of the data use agreement.

NCHS does all it can to assure that the identity of data subjects cannot be disclosed; all direct identifiers, as well as

characteristics that might lead to identifications, are omitted from the data set. Nevertheless, it may be possible in rare

instances, through complex analysis, and with outside information to ascertain from the data sets the identity of particular

persons or establishments. Considerable harm could ensue if this were done.

Therefore, the undersigned gives the following assurances with respect to all NCHS data sets:

. I will not use nor permit others to use the data in these sets in anyway except for statistical reporting and analysis;

● I will not release nor permit others to release the data sets or any part of them to any person who is not a member

of this organization, except with the approval of NCHS;

● I will not attempt to Iink nor permit others to attempt to link the data set with individually identifiable records

from any other NCHS or non-NCHS data set,

. I will not attempt to use the data sets to learn the identity of any person or establishment included in any set; and

. If the identity of any person or establishment should be discovered inadvertently, then (a) no use will be made of

this knowledge, (b) the Director of NCHS will be advised of the incident, (c) the information that would identify

an individual or establishment will be safeguarded or destroyed as requested by NCHS, and (d) no one else will be

informed of the discovered identity.

My signature indicates my agreement to comply with the above-stated statutorily-based requirements with the

knowledge that deliberately making a false statement in any matter within the jurisdiction of any department or agency of

the Federal Government violates 1S U.S.C. 1001 and is punishable by a fine of up to $10,000 or up to 5 years in prison.

Signed: Date:

Print or Type Name:

Title:

Organization:

Address:

City: State: zip:

Phone Number: ( )

tr US. GOVERNMENT PRINTING OFFICE 1992 – 3 I z -082 / 60009
Vital and Health Statistics

series description

SERIES 1.

SERIES 2.

SERIES 3.

SERIES 4.

SERIES 5.

SERIES 6.

SERIES 10.

SERIES 11.

SERIES 12.

SERIES 13.

SERIES 14.

Programs and Collection Procedures – Reports

describing the general programs of the National Center for

Health Statistics and its offices and dlwslons and the data

collection methods used. They also include defmltlons and

other material necessa~ for understanding the data.

Data Evaluation and Methoda Research – Studies of new

statistical methodology including experimental tests of new

survey methods, studies of vital statlsttcs collection

methods, new analytical techniques, objective evaluations

of reliability of collected data, and contributions to statistical

theory. Stud!es also include comparison of U.S.

methodology with those of other countnes.

Analytical and Epidemiological Studies – Reports

presenting analytical or interpretive studies based on vital

and health statistics, carrying the analysis further than the

exposito~ types of reports m the other series.

Documents and Committee Reports – 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 cerhficates.

Comparative International Vital and Health Statistics

Reports -Analytical and descriptwe reports comparing

U.S. wtal and health statistics wkh those of other countries.

Cognition and Survey Measurement– Reports from the

National Laboratory for Collaborate Research in Cognition

and Survey Measurement using methods of cognitive

science to daslgn, evaluate, and test survey instruments.

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 interview survey.

Data From the National Heslth Examination Survey and

the National Health and Nutrition Examination Survey –

Data from direct exammation, testing, and measurement of

national samples of the crwlian noninstlut!onallzed

population prowde the basis for (1) estimates of the

medically defined prevalence of specific dtseases m the

United States and the distributions of the population wrth

respect to physical, physiologlcal, and psychological

characteristlca and (2) anaiysls of relationships among the

various measurements without reference to an explicit fmlte

universe of persons.

Data From the Institutionalized Population Surveys –

Discontinued m 1975. Repofls from these surveys are

included in Series 13.

Data on Health Resources Utilization –Statistics on the

utilization of health manpower and facilities providing longterm care, ambuiatoy care, hospital care, and family

planmng serwces.

Data on Health Resources: Manpower and Facilities –

Statistics on the numbers, geographic dlstnbutlon, and

characteristics of health resources including physicians,

dentists, nurses, other health occupations, hospitals,

nursing homes, and outpatient fachties.

SERIES 15.

SERIES 16.

SERIES 20.

SERIES 21.

SERIES 22.

SERIES 23.

SERIES 24.

Data From SpeciaI 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.

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.

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.

Data on Natslity, Marriage, and Divorce–Various

statistics on natality, marriage, and divorce other than

those included in regular annual or monthly reports.

Special analyses by demographic variables; geographic

and time series analyses; studies of fertility; and statistics

on characteristics of births not available from the vital

records based on sample surveys of those records.

Data From the National Mortality and Natafity Surveys–

Discontinued in 1975. Reports from these sample surveys

based on vital records are included in Series 20 and 21,

respectively.

Data From the National Survey of Family Growth –

Statistics on fertility, family formation and dissolution, family

planning, and related maternal and infant health topics

derived from a periodic survey of a nationwide probability

sample of women 15-44 years of age.

Compilations of Data on Natality, MortaIity, Marriage,

Divo;ce, and Induced Termina~ons of PregnancyAdvance 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 Repofi (MVSR). These reports are

followed by the publication of detailed data in Vital

Statistics of 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 the Vital

and Health Statistics Series.

For answers to questions about this report or for a list of titles of reports

pubiished in these series, contact:

Scientific and Technicai Information Branch

National Center for Health Statistics

Centers for Disease Control

Public Health Service

6525 Belcrest Road, Room 1064

Hyattsville, Md. 20782

301-436-8500
DEPARTMENT OF

HEALTH & HUMAN SERVICES

Public Health Serwce

Centers for Disease Control

National Center for Health Statlstlcs

6525 Belcrest Road

Hyattsvllle, Maryland 20782

OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE, $300

BULK RA-rE

POSTAGE & FEES PAID

PHS/NCl-lS

PERMIT NO. G-281

DHHS Publication No. (PHS) 92-1928, Series 21, No. 50