Series 21

No. 55

Triplet Births:

Trends and

Outcomes, 1971–94

January 1997

Vital and

Health Statistics

From the CENTERS FOR DISEASE CONTROL AND PREVENTION / National Center for Health Statistics

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Public Health Service

Centers for Disease Control and Prevention

National Center for Health Statistics
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

Martin JA, MacDorman MF, Mathews TJ. Triplet births: trends and outcomes,

1971–94. National Center for Health Statistics. Vital Health Stat 21(55). 1997.

Library of Congress Cataloging-in-Publication Data

Martin, Joyce A., M.P.H.

Triplet births: trends and outcomes, 1971–94 / [by Joyce A.

Martin, Marian F. MacDorman, and T. J. Mathews.

p. cm. — (DHHS publication ; no. (PHS) 97-1933) (Vital and

health statistics. Series 21, Data on natality, marriage, and

divorce ; no. 55)

‘‘February 1997.’’

Includes bibliographical references.

ISBN 0-8406-0524-2

1. Triplets—United States—Statistics. 2. Multiple births—

United States—Statistics. I. MacDorman, Marian F. II. Mathews,

T. J. III. National Center for Health Statistics (U.S.) IV.

Series. V. Series: Vital and health statistics. Series 21,

Data from the national vital statistics system ; no. 55.

HA211.A3 no. 55 RG698.U6

304.6'3'0973021 s—dc21

[304.6'3'0973] 96-50049

CIP

For sale by the U.S. Government Printing Office

Superintendent of Documents

Mail Stop: SSOP

Washington, DC 20402-9328

Printed on acid-free paper
Triplet Births:

Trends and

Outcomes, 1971–94

Series 21:

Data From the

National Vital Statistics System

No. 55

Vital and

Health Statistics

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Public Health Service

Centers for Disease Control and Prevention

National Center for Health Statistics

Hyattsville, Maryland

January 1997

DHHS Publication No. (PHS) 97-1933
National Center for Health Statistics

Edward J. Sondik, Ph.D., Director

Jack R. Anderson, Deputy Director

Jack R. Anderson, Acting Associate Director for

International Statistics

Lester R. Curtin, Ph.D., Acting Associate Director for

Research and Methodology

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

Epidemiology, and Health Promotion

Gail F. Fisher, Ph.D., Associate Director for Data Standards,

Program Development, and Extramural Programs

Edward L. Hunter, Associate Director for Planning, Budget,

and Legislation

Jennifer H. Madans, Ph.D., Acting 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

Division of Vital Statistics

Mary Anne Freedman, Director

Stephanie J. Ventura, Acting Chief, Natality, Marriage and

Divorce Statistics Branch

Nicholas F. Pace, Acting Chief, Systems and Programming

Branch
Abstract

Objectives—This report describes changes in the number

and ratio of live births in triplet and other higher order

multiple deliveries from 1971 to 1994 by maternal race, age,

education, and marital status. The report also examines the

birth outcomes of triplets compared with singletons, including

overall gestation specific, and birthweight specific infant mortality rates.

Methods—Birth data are obtained from the U.S. certificates of live birth. Mortality data were obtained from the

Linked Birth and Infant Death Data Sets for the 1983–91 birth

cohorts. Most analyses are based on triplet and other higherorder multiple births (quadruplet and quintuplet and greater

births) in the aggregate. (Triplet births comprise about 92 percent of all higher order multiple births.) Triplet and other

higher order birth ratios for most variables are computed by

combining data for years 1982–84 and 1992–94, and for infant

mortality by combining birth cohorts for years 1987–91.

Findings—Between 1971 and 1994 the number and ratio

of triplet births quadrupled, rising from 1,034 to 4,594, and

from 29.1 to 116.2 per 100,000 live births. Most of the

increase was among births to white mothers, particularly

among married and more educated mothers. Only about

one-third of the increase in triplet birthing among white

mothers between 1989 and 1994 could be attributed to changes

in the maternal age distribution. Massachusetts reported the

highest triplet birth ratio (215.9), more than twice the U.S.

ratio (105.5). Other States with comparatively high ratios were

New Hampshire, New Jersey, and Iowa. Nine of 10 triplets

were born preterm compared with 1 of 10 singletons. The

average triplet weighed 1,698 grams at birth, one-half that of

the average singleton (3,358 grams). Triplets were about 12

times more likely to die during the first year of life as

singletons, but had a survival advantage over singletons at

lower gestations and birthweights.

Keywords: triplet births v higher order multiple births v birth

certificate v triplet infant health v triplet infant mortality

iii
Contents

Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

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

Introduction............................................................................................ 2

Methods............................................................................................... 3

Results................................................................................................ 5

Trends in triplet births................................................................................. 5

Maternal race and ethnicity ........................................................................... 5

The effect of the changing maternal age distribution....................................................... 5

Age-specific birth ratios.............................................................................. 6

Maternal educational attainment and marital status........................................................ 6

Mothers’ State of residence ........................................................................... 7

Birth outcomes ...................................................................................... 7

Period of gestation and birthweight .................................................................... 7

Trends in infant mortality ............................................................................ 7

Infant mortality by gestation and birthweight ............................................................ 8

Five leading causes of infant death..................................................................... 8

Discussion ............................................................................................. 9

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

List of detailed tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Text tables

A. Numbers of triplet, quadruplet, and quintuplet and other higher order multiple births: United States, 1989–94 ....... 3

B. Mean birthweight for triplet and other higher order multiple births and singleton births by length of gestation:

United States, 1992–94 total.......................................................................... 7

Figures

1. Observed and age-adjusted birth ratios for triplet and other higher order multiple births by race of mother,

1980–94 ......................................................................................... 5

2. Triplet and other higher order multiple birth ratios by age of mother, 1972–74, 1982–84, and 1992–94 ............ 6

3. Triplet and other higher order multiple birth ratios for married mothers 30–39 years of age by education, 1982–84

and 1992–94 ...................................................................................... 6

4. Birthweight distributions for triplet and other higher order multiple births and singleton births, 1992–94............ 7

v
Triplet Births: Trends and

Outcomes, 1971–94

by Joyce A. Martin M.P.H; Marian F. MacDorman Ph.D.;

and T. J. Mathews, M.S., Division of Vital Statistics

Highlights

The number of live births in triplet and other higher order

multiple deliveries tripled between 1980 (1,337) and 1994

(4,594) and quadrupled between 1971 (1,034) and 1994. Over

the last decade (1985–94), increases in the number of triplets

averaged 11 percent a year.

The triplet and other higher order birth ratio (the number

of triplet and other higher order multiple births per 100,000

live births) rose 214 percent between 1980 and 1994, from

37.0 to 116.2. Steady, sizable increases averaging 12 percent a

year were reported for 1987–94.

The overall rise in the triplet and other higher order

multiple birth ratio (or triplet birth ratio) can be attributed

almost exclusively to the rise in triplet births to white mothers,

among whom the ratio rose 252 percent (from 37.6 to 132.2)

between 1980 and 1994.

About one-third of the increase in the triplet birth ratio

among white mothers can be explained by changes in the

maternal age distribution. The likely explanation for the

remaining two-thirds of the increase is the rise in the use of

fertility-enhancing drugs and techniques.

Among black mothers, the triplet birth ratio rose by a

more modest 52 percent (from 37.1 to 56.3). Most of the

increase among black mothers is fairly recent, occurring since

the mid- to late-1980’s.

Massachusetts reported the highest triplet birth ratio for

1992–94, 215.9, more than twice as high as that of the Nation

as a whole. Ratios were also comparatively high for New

Hampshire, New Jersey, and Iowa.

Triplet births are at much greater risk than singletons of

poor birth outcome. More than 9 of 10 triplet births were born

preterm (less than 37 competed weeks of gestation) compared

with fewer than 1 of 10 singleton infants. The average weight

of a triplet newborn (3 pounds 12 ounces or 1,698 grams) was

one-half that of a singleton newborn (7 pounds 6 ounces or

3,358 grams). The infant death rate for triplet and other higher

order multiple births was 12 times higher than that for

singletons (93.7 compared with 7.8 infant deaths per 1,000

live births), but triplets generally held a survival advantage

over singletons at lower birthweights and shorter gestations.

1
Introduction

This report describes changes in the number and ratio of

live births in triplet and other higher order multiple deliveries

between 1971 and 1994 by maternal race, age, education, and

marital status. The report also examines the birth outcomes

and infant mortality of newborn triplets compared with newborn singletons.

National information on the plurality of births based on

data derived from birth certificates has been published annually by the National Center for Health Statistics (NCHS) since

1917. (Excepted are data years 1969 and 1970 for which

plurality data are not available.) NCHS also has published

additional, more detailed reports on the subject (1,2). These

reports focused on births in twin deliveries as opposed to

births in triplet and other higher multiple deliveries (from now

on referred to as ‘‘triplet births’’ or ‘‘triplets’’) because twin

births comprise the vast majority of multiples, and because of

the small number of triplet births at the time these reports were

written. However, the recent, rapid rise in the number and ratio

of triplet births, has heightened the interest in, and the

feasibility of studying triplets independently.

Although data are available for selected years, NCHS has

not published recent annual infant mortality rates by plurality

from the linked birth and death data sets. Two early NCHS

studies did, however, present rates for singleton and plural

births based on the 1950 and 1960 birth cohorts (3,4).

The general literature includes a number of recent reports

(published since 1990) on multiple births based on national

vital records (5–14); only one of these reports focuses exclusively on triplets (9). This is the first NCHS report to focus on

triplet births.

This report was prepared in the Division of Vital Statistics (DVS). The

authors gratefully acknowledge the assistance of Selma M. Taffel who is as

generous as ever with her time and insight. We would also like to thank

Robert L. Heuser, Chief (retired), Stephanie J. Ventura, Acting Chief of the

Natality, Marriage, and Divorce Statistics Branch, DVS, and John L. Kiely,

Chief, Infant and Child Health Studies, Division of Health and Utilization

Analysis for their helpful comments. This report was edited by Thelma W.

Sanders and typeset by Jacqueline M. Davis of the Publications Branch,

Division of Data Services.

2
Methods

Birth data for this analysis were obtained from birth

certificates from all States and the District of Columbia for

1985–94. The data are provided to NCHS through the Vital

Statistics Cooperative Program (VSCP). From 1972 to 1984

the VSCP included varying numbers of States that provided

data based 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. For 1971 data were

based on a 20- to 50-percent sample of births. The data sets

include births of U.S. residents occurring in the United States,

but excludes births and deaths of U.S. residents occurring

outside the United States.

Mortality data were obtained from the Linked Birth and

Infant Death Data Sets for the 1983–91 birth cohorts. In

these data sets, the death certificate is linked with the corresponding birth certificate for each infant who dies in the

United States. For example, the 1991 birth cohort file includes

infants born in 1991 who died in 1991 or 1992. The linked file

is constructed as a cohort file, with a one-to-one match of birth

and death records from the NCHS annual Natality and Mortality

Vital Statistics Files (15). For more detailed information see

Public Use Tape Documentation: Linked Birth/Infant Death

Data Set (16).

The practice of matching live birth and fetal death records,

which made it possible to determine the number of sets of

multiple births, was discontinued on the national level beginning with data year 1959. This report, therefore, refers only to

individual live births or deaths in triplet and other higher order

multiple birth deliveries, NOT to sets of triplets. For example,

a delivery resulting in two live births and one stillbirth would

be reported as two live births in a triplet delivery, or two triplet

births. Thus, the number of triplet sets cannot be derived from

these data.

For much of the period covered by this report (1978–88)

triplet births were not differentiated from quadruplet and

quintuplet and higher order multiple births in the coding

process for the birth or linked birth-infant death data sets.

Thus, most analyses in this report are based on triplet and

other higher order multiple births in the aggregate. Triplet

births, however, comprise the bulk of higher order multiple

births (92 percent for 1989–94). Therefore, the category ‘‘triplet and other higher order multiple births’’ primarily represents

triplet births (table A).

The triplet birth ratio is defined as the number of triplet

births per 100,000 live births. Three years of data are combined to compute triplet birth ratios for a number of variables

in order to generate statistically reliable rates. Data for years

1982–84 are combined and, when appropriate, compared with

data for years 1992–94. Similarly, more detailed infant mortality rates (defined as the number of infant deaths under 1

year of age per 1,000 live births) combine data for birth

cohorts 1987–91.

National data for births to unmarried women are derived

from two sources. For 1994 marital status is reported directly

on the birth certificate of 45 States and the District of

Columbia. For 1992–93 marital status is reported directly on

the birth certificate of 44 States and the District of Columbia,

and for 1982–84 marital status was reported directly on the

birth certificates of 41 States and the District of Columbia. For

the remaining States, marital status was inferred from comparison of the child’s and parent’s surnames.

For 1982–84 educational attainment of the mother was

not reported for three States: California, Texas, and Washington. For 1992–94 this item was available for all 50 States and

the District of Columbia. Triplet birth ratios for 1992–94 by

age, education, and marital status are presented for both the

entire reporting area (50 States and the District of Columbia),

and for a 47-State and the District of Columbia reporting area.

To maintain consistent reporting areas between time periods

(1982–84 and 1992–94), all analyses are based on the 47-State

area.

Trend data by race in this report are tabulated by race of

mother for all years. References to white births and white

mothers or black births and black mothers are used interchangeably. Trends and characteristics of triplet births among racial

or ethnic groups other than white and black are not presented

because of small numbers or, as in the case for Hispanic births,

Table A. Numbers of triplet, quadruplet, and quintuplet and other

higher order multiple births: United States, 1989–94

Year Triplets Quadruplets

Quintuplets

and other

higher order

multiples

Triplets as

percent of

all triplet

and other

higher

order

multiple births

1994 .............. 4,233 315 46 92

1993 .............. 3,834 277 57 92

1992 .............. 3,547 310 26 91

1991 .............. 3,121 203 22 93

1990 .............. 2,830 185 13 93

1989 .............. 2,529 229 40 90

3
because of substantial changes in the size and composition of

the reporting area over the study period. (Hispanics can be of

any race.) Where the race of mother is missing from the birth

record, it is imputed according to the race of the mother of the

previous record with known race (17).

The effects of changes in the maternal age distribution on

triplet birth ratios for 1980–94 are eliminated using direct

standardization. The 1980 distribution of births by age of

mother is used as the standard population. Standardization was

performed separately by race of mother.

The period of gestation is computed from the first day of

the last normal menstrual period (LMP), as reported by the

mother, to the date of birth. When the LMP is not stated or is

inconsistent with birthweight, the ‘‘clinical estimate of gestation’’ or the birth attendants’ estimate of gestational age is

used.

4
Results

Trends in triplet births

There were 4,594 live births in triplet deliveries in 1994,

triple the number born during the early 1980’s and more than

quadruple the number of 1971 (table 1). The incidence of

triplet birthing accelerated between 1971 and 1994; increases

averaged about 2 percent a year for the 1970’s, 7 percent for

the early 1980’s, and 11 percent from 1985 to 1989. During

the first half of the 1990’s, the number of triplet births

continued to rise rapidly despite a decline in singleton births.

As a result, there were more triplets born over this 5-year

period than for the entire decade of the 1980’s.

As would be expected, the triplet birth ratio also rose over

this period, and at only a slightly slower pace than the number

of triplet births. The 1994 ratio of 116.2 per 100,000 was twice

the 1987 ratio of 56.2, and 4 times the 1971 ratio of 29.1.

Steady, sizable increases averaging 12 percent a year were

reported for 1987–94.

Maternal race and ethnicity

The steep increase in the overall triplet birth ratio can be

attributed almost exclusively to the rise in triplet births among

white mothers. Throughout the study period about 80 percent

of all births were to white mothers. However, from 1971 to

1994, the percent of triplet births to white mothers increased

from 81 to 90 percent. Among white mothers, the rise in the

triplet birth ratio was even more pronounced than the rise

overall. The triplet ratio among white births was 132.2 for

1994, nearly 5 times the ratio in 1971 (28.4), and double that

reported only 6 years earlier (66.0 in 1988). Between 1990 and

1994 alone, the ratio rose 65 percent.

Triplet birth ratios for black and white mothers were quite

similar during the 1970’s and early 1980’s, but ratios for

subsequent years diverged sharply. Ratios for black triplet

births fluctuated during the 1970’s and 1980’s, but rose by

52 percent between 1980 and 1994, from 37.1 to 56.3 (compared with a 252 percent increase in white triplet births, from

37.6 to 132.2). Growth in the ratio among black mothers

appears to be increasing for the most recent years; between

1990 and 1994 ratios increased 20 percent, rising from 46.9 to

56.3 per 100,000.

More recent triplet birth ratios among white mothers

undoubtably would be even higher if not for the increasing

influence of births of Hispanic origin. Although reliable ratios

are not available for much of the study period, triplet births

appear to be much rarer among white Hispanic mothers than

among non-Hispanic white mothers. For 1994 the nonHispanic white triplet birth ratio was 152.6, 3 times as high as

the ratio among white Hispanic mothers of 52.3, and 15 percent higher than the ratio including Hispanic mothers (132.2).

The effect of the changing maternal age distribution

The proportion of mothers aged 30 years and over who

gave birth in 1994 was much higher than in 1980 (34

compared with 20 percent); the result of delayed childbearing

and an aging female population. This upward shift in the

maternal age distribution would be expected to have a positive

influence on triplet birth ratios because the risk of multiple

birth increases with maternal age until about the age of 40

(18). (This is believed to occur as a result of the heightened

levels of gonadotropin hormones of older mothers (18).) A

second factor widely recognized to have a positive effect on

the triplet birth ratio is fertility-enhancing therapies such as

ovulation-enhancing drugs and assisted reproductive techniques (for example, in vitro fertilizations) (19). These therapies, which are more likely to result in triplet births and are

more commonly used by older white women, became more

widespread during the 1980’s (20).

Direct standardization was used to separate the effect of

the older maternal age distribution from that of other potential

influences on triplet birth ratios between 1980 and 1994.

Figure 1 represents the observed and age-adjusted triplet birth

1980 1985 1990 1994

Year

30

Per 100,000 live births

White

Adjusted

Black Observed

Observed

Adjusted

135

50

100

Figure 1. Observed and age-adjusted birth ratios for triplet and

other higher order multiple births by race of mother, 1980–94

5
ratios by maternal race from 1980 to 1994. After standardization for maternal age, the triplet birth ratio for white births in

1994 was 102.1 (compared with the observed or unadjusted

ratio of 132.2). That is, given a maternal age distribution for

1994 similar to that of 1980, the triplet birth ratio would be

about one-fourth lower than the actual ratio or, put another

way, the changing maternal age distribution explains about

one-third of the increase in triplet birth ratios among white

mothers from 1980 to 1994.

The adjustment reveals that the changing age distribution

had a slightly greater impact on triplet birth ratios among

black mothers. Standardization resulted in an age-adjusted

level of 49.1, compared with the observed ratio of 56.3,

indicating that about two-fifths of the increase in the black

births can be attributed to this cause.

Age-specific birth ratios

Sharp rises in age-specific triplet birth ratios among older

mothers over the study period also suggest the influence of

factors other than a shifting maternal age distribution on

overall triplet birth ratios (table 2 and figure 2). Between

1982–84 and 1992–94 triplet birth ratios increased for each

age group, but increases were the most pronounced among

mothers 30 years of age and over. Triplet birth ratios more

than tripled for mothers 35–39 years of age, rising from 67.8

to 216.1 and nearly tripled for mothers 30–34 years of age,

rising from 68.6 to 193.6. Comparatively, the triplet birth ratio

for mothers 25–29 years of age doubled, and that for mothers

aged 20–24 years rose by only 17 percent.

The number of triplet births born to women in their forties

between 1982 and 1984 was too small (only 15) to allow for

the computation of stable ratios and for comparison of these

ratios with those for 1992–94. However, it should be noted

that there has been a large increase in the number of triplet

births to women in this age group, and this increase is far in

excess of the rise in singleton births. For 1992–94 the number

of triplet births to mothers 40–49 years of age (379 births) was

25 times as high as the number born to their counterparts in

1982–84 (15 births). In contrast, the number of singleton

births to mothers in this age group was 2.3 times as high.

Among white mothers, a similar, albeit stronger rise in

age-specific ratios among mothers 30 years of age and over

was observed. Increases for all age groups were substantially

less pronounced among black mothers. The largest increases

among black mothers were, however, also among older mothers 35–39 years of age.

Maternal educational attainment and marital status

Increases in triplet birth ratios between 1982–84 and

1992–94 were most pronounced among married, collegeeducated mothers 30 years of age and over. (Table 3 includes

triplet birth ratios by race, age, education, and marital status

for 1992–94 for two reporting areas, one for the entire United

States, and the other for the 47-State reporting area for which

comparable data are available for 1982–84 and 1992–94. All

analyses in the report are based on ratios derived from the

47-State reporting area, see Sources and methods.) Among all

married women, there was a more than threefold rise in the

birth ratio (from 47.9 to 151.4) in contrast with only a

14 percent rise in the ratio among unmarried mothers (from

32.5 to 37.1). Ratios for married mothers in their twenties

doubled, while levels among mothers in their thirties more

than tripled.

Increases were observed in triplet birth ratios between

1982–84 and 1992–94 across all educational levels, but the

largest were found among women with more education. Again,

increases were largely restricted to married mothers. Over this

time period, triplet birth ratios increased 67 percent among

married mothers with less than a high school education,

173 percent for mothers with at least 12 years of school, and

224 percent for college-educated mothers (at least 16 years of

education). Increases for each educational level were most

elevated for mothers aged 30–39 years (figure 3). Ratios more

than tripled among married mothers in their thirties in each

educational category except for those with less than a high school

education that rose by a comparatively modest 72 percent.

Under 20 20 24 25 29 30 34 35 39 40 44

Years of age

0

50

100

150

200

250

Per 100,000 live births

1972 74 1982 84 1992 94

Figure 2. Triplet and other higher order multiple birth ratios by

age of mother, 1972–74, 1982–84, and 1992–94

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

0 11 years 12 years 13 15

years

16 years

or more

0

50

100

150

200

250

300

350

Per 100,000 live births

1982 84 1992 94

Education

Figure 3. Triplet and other higher order multiple birth ratios for

married mothers 30–39 years of age by education, 1982–84 and

1992–94

6
Trends in triplet birth ratios by marital status and educational attainment among white mothers between 1982–84 and

1992–94 were similar to those noted earlier, but generally

were of greater magnitude. Among black mothers, trends were

generally analogous, but considerably more modest. Although

rises in the triplet birth ratio overall among black unmarried

mothers were greater than for white unmarried mothers, these

data suggest that the largest increases among black mothers

were also among those who were older, married, and more

educated.

Mothers’ State of residence

Massachusetts reported the highest triplet birth ratio for

combined years 1992–94 (215.9) more than twice as high as

that of the Nation as a whole (105.5) (table 4). The Massachusetts ratio was substantially higher than that of any other State

for both 1993 and 1994, and was the third highest for 1992.

Other States reporting ratios at least 50 percent higher than the

United States for 1992–94 were New Hampshire, New Jersey,

and Iowa. These States also tended to have higher proportions

of births to older mothers who are more likely to have a triplet

birth, and to older, white non-Hispanic mothers who may be

more likely to obtain fertility-enhancing drugs and procedures,

further increasing their chances of bearing triplets (20).

Birth outcomes

Period of gestation and birthweight

The mean or average gestational age for triplet infants

was 32 completed weeks, almost 7 weeks shorter than the

average for singleton births (table 5). The most common

gestational age for triplets was 34–36 weeks, while that for

singletons was 37–41 weeks. Accordingly, most triplets

(91.6 percent) were born preterm, that is, at fewer than 37

completed weeks of gestation, compared with 9.8 percent of

singleton infants. Moreover, 13.4 percent of triplets were born

at the extremely preterm gestational age of less than 28 weeks,

whereas only 0.6 percent of singletons were born at this short

gestational age.

The average triplet weighed 3 pounds, 12 ounces (1,698

grams) at birth, one-half that of the average singleton infant (7

pounds, 6 ounces or 3,358 grams) (table 6). Because preterm

infants weigh less than term infants, the smaller size of triplet

births can be partly explained by their shorter gestations, but

large differences in birthweight between triplets and singletons

persist at similar or equal gestations. At each completed week

of gestation except the shortest (17 weeks), the average

birthweight for triplets was lower than that of singletons (data

not shown). The greatest absolute and relative disparities in

triplet and singleton birthweight, however, were for term and

postterm births (those born at 37–41 weeks and at 42 and more

weeks of gestation). In illustration, the average birthweight for

triplet term births was 1,202 grams less or 35 percent lower

than that for singleton births (2,224 grams compared with

3,426 grams, table B).

Overall, 92.1 percent of triplets born between 1992 and

1994 were low birthweight (less than 2,500 grams); and

35.0 percent were very low birthweight (less than 1,500

grams) (figure 4). The respective proportions for singleton

infants were 6.0 and 1.1 percent. At no gestational age was the

average triplet birthweight greater than 2,499 grams. Most

triplets, 86.0 percent, are born both low birthweight and

preterm; only 6.2 percent were term low-birthweight infants

(data not shown).

Triplets born to black mothers (unlike singleton births to

black mothers) were slightly less likely than triplets born to

white mothers to be preterm (88.2 compared with 91.1 percent), but were nearly twice as likely to be born at less than 28

weeks (22.4 compared with 12.7 percent). Triplets born to

black mothers were slightly smaller on average than those

born to white mothers (1,537 compared with 1,712 grams) and

were more likely to be very low birthweight; nearly one-half

of all black triplets (45.4 percent) weighed less than 1,500

grams compared with 34.1 percent of white triplets (tables 5

and 6).

Less

than 500

2,000 

 2,499

4,000

or more

Grams

0

10

20

30

40

Percent

Triplets

Singletons

Figure 4. Birthweight distributions for triplet and other higher

order multiple births and singleton births, 1992–94

Table B. Mean birthweight for triplet and other higher order

multiple births and singleton births by length of gestation:

United States, 1992–94 total

Period of gestation1 Triplet2 Singleton

Difference

in grams

Percent

difference

Mean

All gestations......... 1,698 3,358 –1,660 –49

Under 28 weeks. . . . . . . 731 961 –230 –24

28–31 weeks......... 1,347 2,054 –707 –34

32–33 weeks......... 1,755 2,497 –742 –30

34–36 weeks......... 2,109 2,898 –789 –27

37–41 weeks......... 2,224 3,426 –1,202 –35

42 weeks or more...... 2,203 3,525 –1,322 –38

1Completed weeks of gestation.

2Includes births in quadruplet, and quintuplet and other higher order multiple deliveries.

7
Trends in infant mortality

From 1983 to 1991 infant mortality rates for triplet births

declined by 40 percent, from 156.1 infant deaths per 1,000 live

births to 93.7 for 1991 (table 7). This decrease was greater

than the 28 percent decrease among singletons (from 10.9 in

1983 to 7.8 in 1991). Infant mortality rates for triplet births to

white mothers declined more rapidly and were generally

substantially lower than those for triplet births to black

mothers, although small numbers of black infant deaths have

led to large fluctuations in infant mortality rates for this group.

Infant mortality by gestation and birthweight

In recent years triplet infants have been about 12 times

more likely to die during the first year of life as singleton

infants. Much of the difference in mortality can be explained

by triplets’ considerably shorter gestations and lower birthweights (see section on Period of gestation and birthweight).

For combined years 1987–91, birthweight-specific mortality

rates through 2,500 grams for triplets were comparable to, or

were more favorable than those for singletons (table 8). Below

birthweights of 1,000 grams, mortality rates were similar for

triplets and singletons, but at 1,000–2,499 grams, triplets held

a distinct survival advantage. For example, at birthweights of

1,500–1,999 grams, the triplet infant mortality rate was 15.2

per 1,000 compared with a singleton rate of 50.4.

Among all triplet births, mortality was lowest at birthweights of 2,000–2,499 grams, whereas among singletons, the

most favorable mortality rate was for heavier babies with

birthweights of at least 2,500 grams. (Although considered

unreliable because it is based on only 15 deaths, the rate for

triplets with birthweights of 2,500 grams or more (11.4) is

higher than that for triplets born at 2,000–2,499 grams (7.3),

and for singletons born at 2,500 grams or more (3.7)).

Triplet mortality rates by gestation follow a pattern not

unlike that of birthweight (table 9). For gestations of less than

28 weeks, the infant mortality rate was higher among triplets

than for singletons (628.8 compared with 402.1 per 1,000), but

for longer gestations of up to 36 weeks, triplet mortality rates

were similar to, or more favorable than those for singletons.

For instance, at 32–33 weeks, the triplet mortality rate of 17.9

was 33 percent lower than the singleton rate (26.8). Conversely, triplet births born at term were at greater risk of

mortality than singleton term births (21.5 compared with 4.0).

Whereas, among singleton births infant mortality rates

decline steadily with increasing gestation, mortality rates

among triplets decline to 34–36 weeks, but rise for births born

at term. As a result, for triplet births overall, the lowest

mortality was among moderately preterm births of 34–36

weeks of gestation, whereas singleton mortality was most

favorable among term births.

Five leading causes of infant death

The five leading causes of infant death were the same for

triplets as for singletons, but the order of the causes was very

different (table 10). The leading cause of death for triplets was

Newborn affected by maternal complications of pregnancy

(maternal complications), followed by Respiratory distress

syndrome (RDS), Disorders relating to short gestation and

unspecified low birthweight (short gestation and low birthweight), Congenital anomalies, and Sudden infant death syndrome (SIDS). For singletons, the leading cause of death was

Congenital anomalies, followed by SIDS, short gestation and

low birthweight, RDS, and maternal complications. Of the

triplet records coded to maternal complications as a cause of

death, the majority of these deaths (89 percent in 1991) were

coded to subcategory 761.5—Multiple pregnancy. Cause-ofdeath coding rules require that maternal complications such as

Multiple pregnancy be selected in preference to short gestation

and low birthweight as the underlying cause of death, even if

the physician had listed short gestation and low birthweight as

the underlying cause (21). All triplet records coded to multiple

pregnancy in 1991 also contained multiple cause-of-death

codes for short gestation and low birthweight. If these records

were recoded to short gestation and low birthweight, as has

been done in other studies of multiple deliveries (6), short

gestation and low birthweight would have been the leading

cause of death for triplets.

In general, infant mortality rates for causes of death that

are strongly associated with low birthweight are much higher

among triplets than among singletons. In 1991 at least 97 percent of the deaths from maternal complications, RDS, and

short gestation and low birthweight (the three leading causes

of infant death for triplet and higher order births) were to lowbirthweight infants (data not shown).

8
Discussion

The triplet birth ratio rose 214 percent over the 15-year

period 1980 to 1994. Among white mothers, the ratio rose

252 percent and among black mothers, 52 percent. In comparison, the twin birth ratio rose only 30 percent over this period.

Most of the remarkable rise in the overall triplet birth ratio can

be attributed to increases in triplet births to white mothers who

accounted for 87 percent of all triplet births.

About one-third of the increase in the white triplet birth

ratio can be explained by the change in maternal age at

childbearing. The likely explanation for the remaining twothirds of the increase is the rise in the use of fertilityenhancing drugs and techniques (ovulation-enhancing drugs

and assisted reproductive techniques such as in vitro fertilization), which are more likely to result in triplet births (20 and

22–24) and are more commonly used by older white women

of higher socioeconomic status, the group for which triplet

birth ratios rose the most (20). A recent study estimates that

about 30 percent of the increase in triplet births from the early

1970’s to the early 1990’s can be attributed to the older

maternal age distribution (a proportion similar to that reported

here), 38 percent to artificial reproductive techniques, and the

remaining one-third may be associated with the use of fertilityenhancing drugs (19). Others have estimated that 59–80 percent

of the increase in triplet births are the result of these therapies

(25,26).

Although at a much slower pace, triplet birthing among

black mothers is also on the rise. This study suggests that

much of this increase also is the result of factors other than a

changing maternal age distribution such as fertility-enhancing

therapies. This contrasts with the results of an earlier study

that attributed the growth in the triplet birth ratio among black

mothers from 1972 to 1989 to an older maternal age distribution (9). This discrepancy is most likely the result of the

different time periods studied. Indeed, we found that most of

the increase among black mothers is fairly recent, occurring

since the mid- to late-1980’s. When 3-year average triplet

birth ratios are used, the triplet birth ratio increased 8 percent

between 1980–82 and 1986–88, and 34 percent between

1986–88 and 1992–94.

The steep rise in triplet births (whether the result of

fertility-enhancing techniques) is of concern because of their

high likelihood of permanent disability or early death. (Extensive pregnancy-related morbidity among mothers of triplets

has been reported elsewhere (27).) This study confirms that

triplet births are at greater risk than singletons of poor birth

outcomes, and that much of this excess risk results from

triplets’ shorter gestations and lower birthweights. The vast

majority (92.1 percent) weigh less than 2,500 grams at birth,

and more than one-third less than 1,500 grams; most are born

preterm (91.1 percent), and 13 percent were born at the very

abbreviated gestational length of less than 28 weeks. Associated with the high preterm rate of triplets is their increased risk

of inadequate lung development and greater likelihood of

morbidity (22) or infant death resulting from respiratory

distress syndrome.

The survival advantage which triplets appear to have with

respect to singletons at most shorter gestations and lower

birthweights disappears for gestations of 34 weeks and greater,

and may disappear at birthweights of 2,500 grams and more.

These findings suggest that intrauterine growth may stop

earlier for triplets than for singletons, and, that the optimum

gestational age and birthweight may be shorter and lower for

triplets than for singletons. Indeed, the mean birthweight for

triplets dropped precipitously at 39 weeks, whereas that of

singletons did not begin to decline until the 42d week of

gestation (data not shown). Ellster AD, et al. (26) found that

the 35th week of gestation was the point at which triplet

birthweight began to lag even further behind that of singletons. Similar results have been reported for twin births (24,28).

Whereas data on birthweight and plurality from the birth

certificate are considered reliable (29,30), the accuracy of birth

certificate data on gestational age has been widely questioned

(31). However, comparison of our data on the gestational age

of triplets with that of a study that based its computation of

gestational age on known date of conception by artificial

methods, or by first trimester ultrasonography for patients who

conceived spontaneously, revealed fairly similar average gestational ages (33 compared with 32.2 weeks) and rates of

preterm birth (86.0 compared with 91.1 percent) (27). For

1992–94, gestational age was missing from only 1.0 percent of

the birth records of triplets and 0.9 percent of records of

singleton births. Differences by plurality in the rate of preterm

birth are too great to be substantively affected by potential

differential reporting of gestational age.

In general, the birthweight and gestation measures presented in this report are comparable to, but somewhat lower

than those reported elsewhere (26,27,32). One reason for the

slightly lower levels is that for this study data are derived from

all U.S. births, whereas data for other studies (such as the one

mentioned in earlier text) are often drawn from one medical

center, or are otherwise based on preselected populations

(26,27,32). In addition, because disaggregated data were not

9
available for much of the study period, all findings for triplets

in this study include quadruplet, and quintuplet and other

higher order multiple births (these births accounted for 8 percent of all triplet and other higher order multiple births for

1994 (table A), whereas other studies generally restrict the

analysis to triplet births only.) This is important because

measures of birthweight and gestation that include all higherorder multiple births are slightly different than those for

triplets alone (that is, the percents low birthweight, very low

birthweight, and preterm are higher, and mean birthweight and

gestational age are lower). For example, for 1992–94 the

percent low birthweight for triplets excluding other higher

order multiples was 91.7 and the percent preterm was 90.8,

compared with levels for all higher order multiple births of

92.4 and 91.1 percent.

The majority of the 37,514 triplets born between 1980 and

1994 were most likely the result of fertility-enhancing therapies. Despite declines in infant mortality and a survival

advantage over singletons at shorter gestations and lower

birthweights, about 1 of every 10 of triplet newborns died

within the first year of life. Those who survived were at

greater risk of perinatal complications resulting in lifelong

disability. The precarious health status of triplets and their

rising numbers make further research into these births of

growing importance.

10
References

1. Heuser RL. Multiple births United States - 1964. National

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

2. Taffel SM. Health and demographic characteristics of twin

births: United States, 1988. National Center for Health Statistics. Vital Health Stat 21(50). 1992.

3. Armstrong RJ. A study of infant mortality from linked records

by birth weight, period of gestation, and other variables United

States. National Center for Health Statistics. Vital Health Stat

20(12). 1972.

4. Chase HC. A study of infant mortality from linked records:

Comparison of neonatal mortality from two cohort studies

United States. U.S. Department of Health Education and Welfare. Vital and Health Stat 20(13). 1972.

5. Keith LG, Papiernik E, Luke B. The costs of multiple pregnancy. Int J Gynecol Obstet 36:109–14. 1991.

6. Fowler MG, Kleinman JC, Kiely JL. Double jeopardy: Twin

infant mortality in the United States, 1983 and 1984. Am J

Obstet Gynecol 165(1)15–22. 1991.

7. Kleinman JC, Fowler MG, Kessel SS. Comparison of infant

mortality among twins and singletons: United States 1960 and

1983. Am J of Epidemiol 133(2):133–43. 1991.

8. Luke B, Keith LG. The contribution of singletons, twins and

triplets to low birth weight, infant mortality and handicap in the

United States. J Reprod Med 37(8):661–6. 1992.

9. Kiely JL, Kleinman JC, Kiely M. Triplets and higher-order

multiple births: Time trends and infant mortality. Am J Dis

Child 146:862–8. 1992.

10. Luke B. The changing pattern of multiple births in the United

States: Maternal and infant characteristics, 1973 and 1990.

Obstet Gynecol 84(1) 101–6. 1994.

11. Mushinski M. Trends in multiple births. Stat Bull 75(3):28–35.

1994.

12. Powers WF, Kiely JL. The risks confronting twins: A national

perspective. Am J Obstet Gynecol 170(2):456–61. 1994.

13. Jewell SE, Yip R. Increasing trends in plural births in the United

States. Obstet Gynecol 85(2):229–32. 1995.

14. Martin JA, Taffel SM. Current and future impact of rising

multiple birth ratios on low birthweight. Stat Bull 76(2) 10–8.

1995.

15. Wilcox LS, Marks JS, eds. From data to action: CDC’s public

health surveillance for women, infants, and children. Atlanta,

Georgia: 231–49. Centers for Disease Control and Prevention.

1994.

16. National Center for Health Statistics. Public-use data tape

documentation. Linked birth/death data set: 1987–1991 birth

cohorts. Hyattsville, Maryland: Public Health Service. 1992–95.

17. National Center for Health Statistics. Instruction Manual Part 3a

Classification and coding instructions for live birth records,

1993. Vital Stat. Hyattsville, Maryland: Public Health Service.

1993.

18. Danforth DN. Danforth’s obstetrics and gynecology. 6th ed.

Philadelphia: J.B. Lippincott Co. 1990.

19. Wilcox LS, Kiely JL, Melvin CL, Martin MC. Assisted reproductive technologies: Estimates of their contribution to multiple

births and newborn hospital days in the United States. Fertil

Steril 65(2):361–6. 1996.

20. Wilcox LS, Mosher WD. Use of infertility Services in the

United States. Obstet Gynecol 82 (1):122–7. 1993.

21. World Health Organization. Manual of the International Statistical Classification of Diseases, Injuries, and Causes of Death,

based on the recommendations of the Ninth Revision Conference, 1975. Geneva: World Health Organization. 1977.

22. American College of Obstetricians and Gynecologists. Multiple

gestation. ACOG technical bulletin 131. Washington: American

College of Obstetricians and Gynecologists. 1995.

23. Bollen N, Camus M, Staessen D, et al. The incidence of

multiple pregnancy after in vitro fertilization and embryo

transfer, gamete, or zygote intrafallopian transfer. Fertil Steril

55(2): 314–8. 1991.

24. Keith LG, Papiernik E, Keith DM, Luke B, eds. Multiple

Pregnancy—Epidemiology, gestation, and perinatal outcome.

New York, London: Hecht, 175–90 and Powers, 163–74. The

Parthenon Publishing Group. 1995.

25. Callahan TL, Hall JE, Ettner Sl, et al. The economic impact of

multiple gestation pregnancies and the contribution of assisted

reproductive techniques to their incidence. N Engl J Med

331(4): 244–9. 1994.

26. Ellster AD, Bleyl JL, Craven TE. Birthweight standards for

triplets under modern obstetric care in the United States,

1984–1989. Obstet Gynecol 77(3):387–93. 1991.

27. Albrech JL, Tomich PG. The maternal and neonatal outcome of

triplet gestations. Am J Obstet Gynecol. 174(5):1551–6. 1996.

28. Luke B, Witter FR, Abbey H, et al. Gestational age-specific

birthweights of twins versus singletons. Acta Genet Med Gemollol

(Roma) 40:69–76. 1991.

29. Buescher PA, Pinnex KV, Davis MH, Bowling JM. Quality of

the new birth certificate data: a follow-back study in North

Carolina. Chess Studies 68(6):1–10. 1992.

30. Schoendorf KC, Parker JD, Batkhan LZ, Kiely JL. Comparability of the birth certificate and 1988 Maternal and infant health

survey. National Center for Health Statistics. Vital and Health

Stat. 2(116). 1993.

31. Alexander GR, Tomkins ME, Cornely, DA. Gestational age

reporting and preterm delivery. Public Health Rep 105(2):

267–75. 1990.

32. Sassoon DA, Castro LC, Davis JL, Hobel CJ. Perinatal outcome

in triplet versus twin gestations. Obstet Gynecol. 75(5): 817–20.

1990.

11
List of detailed tables

1. Numbers and ratios of triplet and other higher order

multiple births: United States, 1971–94. . . . . . . . . . . . . 13

2. Triplet and other higher order multiple birth ratios by age

and race of mother: United States, 1972–74, 1982–84, and

1992–94 total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3. Triplet and other higher order multiple birth ratios by age,

education, marital status, and race of mother: Total of 47

reporting States, 1982–84, total of 47 reporting States,

1992–94, and United States, 1992–94 total . . . . . . . . . . 15

4. Triplet and other higher order multiple birth ratios: United

States and each State, 1992–94 total . . . . . . . . . . . . . . . 17

5. Number and percent distribution of triplet and other higher

order multiple births and singleton births by period of

gestation and race of mother: United States, 1992–94

total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6. Number of triplet and other higher order multiple births

and singleton births by period of gestation and percent

distribution by birthweight according to period of gestation and race of mother: United States, 1992–94 total . . 18

7. Infant mortality rates for triplet and other higher order

multiple births and singleton births by race of mother:

United States, 1983–91 birth cohorts ............... 19

8. Infant mortality rates for triplet and other higher order

multiple births and for singleton births by birthweight:

United States, birth cohorts 1987–91 total ........... 20

9. Infant mortality rates for triplet and other higher order

multiple births and for singleton births by period of

gestation: United States, birth cohorts 1987–91 total . . . 20

10. Infant mortality rates for the 5 leading causes of death for

triplet and other higher order multiple births and singleton

births: United States, birth cohorts 1987–91 total ...... 20

12
Table 1. Numbers and ratios of triplet and other higher order multiple births: United States 1971–94

[Ratios are live births in triplet and other higher order multiple birth deliveries per 100,000 total live births]

Year Triplets2

All races1 White Black

Total3

Triplet

birth

ratio Triplets2 Total3

Triplet

birth

ratio Triplets2 Total3

Triplet

birth

ratio

1994 ............. 4,594 3,952,767 116.2 4,127 3,121,004 132.2 358 636,391 56.3

1993 ............. 4,168 4,000,240 104.2 3,748 3,149,833 119.0 327 658,875 49.6

1992 ............. 3,883 4,065,014 95.5 3,444 3,201,678 107.6 361 673,633 53.6

1991 ............. 3,346 4,110,907 81.4 2,905 3,241,273 89.6 368 682,602 53.9

1990 ............. 3,028 4,158,212 72.8 2,639 3,290,273 80.2 321 684,336 46.9

1989 ............. 2,798 4,040,958 69.2 2,483 3,192,355 77.8 262 673,124 38.9

1988 ............. 2,385 3,909,510 61.0 2,048 3,102,083 66.0 286 638,562 44.8

1987 ............. 2,139 3,809,394 56.2 1,821 3,043,828 59.8 246 611,173 40.3

1986 ............. 1,814 3,756,547 48.3 1,585 3,019,175 52.5 199 592,910 33.6

1985 ............. 1,925 3,760,561 51.2 1,648 3,037,913 54.2 240 581,824 41.2

19844 ............. 1,653 3,669,141 45.1 1,416 2,967,100 47.7 195 568,138 34.3

19834 ............. 1,575 3,638,933 43.3 1,319 2,946,468 44.8 216 562,624 38.4

19824 ............. 1,484 3,680,537 40.3 1,199 2,984,817 40.2 240 568,506 42.2

19814 ............. 1,385 3,629,238 38.2 1,188 2,947,679 40.3 172 564,955 30.4

19804 ............. 1,337 3,612,258 37.0 1,104 2,936,351 37.6 211 568,080 37.1

19794 ............. 1,202 3,494,398 34.4 999 2,842,867 35.1 185 557,684 33.2

19784 ............. 1,185 3,333,279 35.6 942 2,713,108 34.7 206 532,825 38.7

19774 ............. 1,076 3,326,632 32.3 899 2,720,183 33.0 164 526,667 31.1

19764 ............. 1,086 3,167,788 34.3 852 2,593,957 32.8 205 498,506 41.1

19754 ............. 1,066 3,144,198 33.9 909 2,576,818 35.3 151 496,829 30.4

19744 ............. 1,005 3,159,958 31.8 812 2,598,222 31.3 171 494,005 34.6

19734 . . . . . . . . . . . . . 944 3,136,965 30.1 751 2,571,660 29.2 169 500,505 33.8

19724 . . . . . . . . . . . . . 907 3,258,411 27.8 733 2,675,535 27.4 156 519,824 30.0

19715 ............. 1,034 3,555,970 29.1 834 2,939,568 28.4 196 553,750 35.4

1Includes races other than white and black.

2Includes births in quadruplet and quintuplet and other higher order multiple deliveries.

3Includes births in twin deliveries.

4Based on 100 percent of births in selected States and on a 50-percent sample of births in all other States.

5Based on a 50-percent sample of births.

13
Table 2. Triplet and other higher order multiple birth ratios by age and race of mother: United States, 1972–74, 1982–84, and

1992–94 total

[Ratios are the number of triplet and other higher order multiple births per 100,000 live births in the specific group]

Age and race of mother

Years Percent change

1982–84 to

1992–94

Percent change

1972–74 to

1992–94 1982–84 1972–74 1992–94

All races1

All ages ................... 105.2 42.9 29.9 145.2 251.8

Under 20 years .............. 14.9 15.0 10.2 –0.7 46.1

20–24 years ................ 35.7 30.5 27.4 17.0 30.3

25–29 years ................ 99.3 50.1 40.0 98.2 148.3

30–34 years ................ 193.6 68.6 41.5 182.2 366.5

35–39 years ................ 216.1 67.8 39.6 218.7 445.7

40–44 years ................ 186.8 * 37.3 * 400.8

45–49 years ................ 672.1 * * * *

White

All ages ................... 119.5 44.2 29.3 170.4 307.8

Under 20 years .............. 12.8 13.0 7.7 –1.5 66.2

20–24 years ................ 35.8 29.8 25.6 20.1 39.8

25–29 years ................ 109.0 51.3 39.6 112.5 175.3

30–34 years ................ 217.3 70.6 40.6 207.8 435.2

35–39 years ................ 236.1 70.8 38.7 233.5 510.1

40–44 years ................ 214.7 * 29.8 * 620.5

45–49 years ................ 735.0 * * * *

Black

All ages ................... 53.1 38.3 32.8 38.6 61.9

Under 20 years .............. 17.6 15.7 16.6 12.1 6.0

20–24 years ................ 40.2 34.5 35.3 16.5 13.9

25–29 years ................ 61.3 49.1 47.5 24.8 29.1

30–34 years ................ 87.5 68.0 48.0 28.7 82.3

35–39 years ................ 127.9 65.6 49.3 95.0 159.4

40–44 years ................ * * * * *

45–49 years ................ * * * * *

*Figure does not meet standards of reliability or precision.

1Includes races other than white and black.

14
Table 3. Triplet and other higher order multiple birth ratios by age, education, marital status, and race of mother: Total of 47

reporting States, 1982–84, total of 47 reporting States, 1992–94, and United States, 1992–94 total

[Ratios are the number of triplet and other higher order multiple births in the specific group]

Education level, race

and age of mother

Total Married Unmarried

1992–941 1992–942 1982–842 1992–941 1992–942 1982–842 1992–941 1992–942 1982–842

All educational levels

All races,3 all ages ..... 105.2 115.1 44.7 136.1 151.4 47.9 37.2 37.1 32.5

Under 20 years ..... 14.9 15.9 15.9 12.8 14.6 16.1 15.7 16.3 15.7

20–29 years ....... 68.9 76.9 41.9 83.7 94.7 42.7 36.1 38.7 38.1

30–39 years ....... 200.0 217.1 71.8 221.3 240.8 72.0 79.1 73.9 70.0

40–49 years ....... 204.7 189.3 * 225.2 212.3 * 112.9 * *

White, all ages ....... 119.5 133.4 46.3 145.8 161.8 48.2 35.3 34.7 32.5

Under 20 years ..... 12.8 13.7 14.6 12.1 14.4 16.0 13.1 13.4 12.5

20–29 years ....... 75.3 85.5 42.4 88.4 100.1 42.9 33.1 35.2 38.1

30–39 years ....... 222.6 242.4 73.6 240.1 259.2 73.1 80.2 76.0 83.7

40–49 years ....... 233.3 217.7 * 250.8 234.0 * 134.3 * *

Black, all ages ....... 53.1 53.0 38.7 79.5 82.2 47.9 41.3 41.0 32.7

Under 20 years ..... 17.5 19.0 16.2 * * * 17.5 18.8 17.1

20–29 years ....... 49.1 50.0 41.5 62.8 63.9 43.6 42.7 44.0 39.7

30–39 years ....... 99.2 95.3 66.2 109.9 111.0 70.5 87.0 78.1 57.9

40–49 years ....... 93.0 * * * * * * * *

0–11 years

All races,3 all ages ..... 33.2 36.7 28.8 40.1 46.4 27.8 27.9 31.1 30.2

Under 20 years ..... 14.5 17.1 13.9 10.3 * 10.4 15.8 18.0 16.1

20–29 years ....... 35.9 41.8 36.0 40.6 47.4 32.0 31.1 37.0 43.4

30–39 years ....... 69.4 82.2 53.9 66.4 80.2 46.7 74.1 85.0 73.5

40–49 years ....... * * * * * * * * *

White, all ages ....... 33.4 38.3 24.4 40.6 47.7 24.2 26.0 29.7 24.8

Under 20 years ..... 13.4 16.6 11.7 10.8 * 10.5 14.7 17.5 13.1

20–29 years ....... 34.8 42.3 29.7 40.5 48.2 28.4 27.0 34.6 34.1

30–39 years ....... 71.0 86.7 45.3 70.3 87.8 39.5 72.3 84.5 *

40–49 years ....... * * * 89.4 * * * * *

Black, all ages ....... 33.2 34.1 38.2 50.6 52.2 51.6 30.9 32.0 34.6

Under 20 years ..... 14.3 15.8 15.0 * * * 14.6 16.3 16.1

20–29 years ....... 42.5 41.3 54.8 * * 54.9 41.3 40.1 54.8

30–39 years ....... 90.0 93.8 82.5 * * 82.7 89.4 95.4 82.2

40–49 years ....... * * * * * * * * *

12 years

All races,3 all ages ..... 76.6 81.4 37.8 96.3 105.6 38.7 38.6 36.4 34.1

Under 20 years ..... 14.5 13.5 18.2 15.3 * 21.4 14.1 13.7 14.5

20–29 years ....... 60.1 66.5 37.0 70.4 80.6 36.6 40.1 40.2 39.4

30–39 years ....... 143.1 146.5 55.0 163.3 170.2 54.9 65.5 55.2 55.8

40–49 years ....... 105.7 88.0 * 118.0 112.5 * * * *

White, all ages ....... 84.4 91.1 37.4 101.1 110.8 37.7 35.5 32.0 35.1

Under 20 years . . . . . 9.7 * 18.3 * * 20.6 * * *

20–29 years ....... 63.8 71.3 36.3 72.7 83.2 36.1 37.1 34.7 38.3

30–39 years ....... 160.2 166.4 53.8 176.2 183.0 52.2 66.5 61.7 76.9

40–49 years ....... 106.4 89.7 * 112.6 109.5 * * * *

See footnotes at end of table.

15
Table 3. Triplet and other higher order multiple birth ratios by age, education, marital status, and race of mother: Total of 47

reporting States, 1982–84, total of 47 reporting States, 1992–94, and United States, 1992–94 total—Con.

[Ratios are the number of triplet and other higher order multiple births in the specific group]

Education level, race

and age of mother

Total Married Unmarried

1992–941 1992–942 1982–842 1992–941 1992–942 1982–842 1992–941 1992–942 1982–842

12 years—Continued

Black, all ages ....... 51.6 52.3 40.4 69.0 76.8 47.6 44.4 43.0 35.2

Under 20 years ..... 23.3 27.0 * * * * 22.2 25.2 *

20–29 years ....... 50.4 52.7 43.1 62.5 67.3 43.8 45.5 47.2 42.6

30–39 years ....... 75.8 69.5 59.4 83.8 93.3 70.6 69.3 50.5 *

40–49 years ....... * * * * * * * * *

13–15 years

All races,3 all ages ..... 119.2 127.3 50.2 138.9 150.7 51.1 44.5 41.3 42.6

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

20–29 years ....... 82.7 88.5 45.3 97.2 105.1 47.4 36.2 37.9 29.7

30–39 years ....... 185.3 200.5 66.6 200.9 219.7 62.6 78.8 67.5 122.9

40–49 years ....... 198.9 175.9 * 218.8 209.9 * * * *

White, all ages ....... 134.7 144.1 53.8 150.4 161.7 52.8 41.1 35.1 70.5

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

20–29 years ....... 92.1 98.8 49.3 103.8 111.8 48.8 33.1 31.9 58.0

30–39 years ....... 207.4 223.3 68.5 219.7 236.9 64.7 74.8 62.3 171.4

40–49 years ....... 217.6 202.8 * 237.6 229.6 * * * *

Black, all ages ....... 65.0 63.8 35.0 80.5 79.5 45.5 51.9 51.7 21.4

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

20–29 years ....... 53.8 53.4 28.4 67.9 62.2 42.1 43.7 47.5 *

30–39 years ....... 98.6 95.4 61.7 102.5 107.0 60.1 92.9 79.1 *

40–49 years ....... * * * * * * * * *

16 or more years

All races,3 all ages ..... 228.7 239.8 75.3 237.4 249.0 76.9 89.1 79.1 *

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

20–29 years ....... 121.8 128.5 58.4 128.6 135.6 60.1 36.3 39.6 *

30–39 years ....... 294.2 312.5 94.3 302.5 320.9 95.7 124.3 110.6 *

40–49 years ....... 316.4 287.9 * 320.7 290.9 * * * *

White, all ages ....... 250.2 259.3 80.1 256.0 265.1 81.0 118.0 103.4 *

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

20–29 years ....... 135.9 141.7 63.6 140.5 146.0 64.3 * * *

30–39 years ....... 318.3 334.1 98.4 324.5 339.9 99.5 150.5 129.6 *

40–49 years ....... 352.3 314.8 * 351.9 312.6 * * * *

Black, all ages ....... 99.8 99.8 36.2 118.1 118.7 40.8 49.6 * *

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

20–29 years ....... 46.4 54.5 * 58.5 70.6 * * * *

30–39 years ....... 144.3 136.8 63.4 157.1 147.7 64.3 * * *

40–49 years ....... * * * * * * * * *

*Figure does not meet standards of reliability or precision.

1Includes 50 States and the District of Columbia.

2Excludes Calfornia, Texas, and Washington that did not report education for 1982–84.

3Includes races other than white and black.

16
Table 4. Triplet and other higher order multiple birth ratios: United States and each State, 1992–94 total

[Ratios are live births in triplet and other higher order multiple birth deliveries per 100,000 total live births]

State Ratio State Ratio

United States ...................... 105.5

Alabama ......................... 78.4

Alaska ........................... *

Arizona .......................... 94.9

Arkansas ......................... 67.4

California ......................... 76.6

Colorado ......................... 127.3

Connecticut ....................... 136.5

Delaware ......................... 123.3

District of Columbia ................... *

Florida ........................... 94.1

Georgia .......................... 72.1

Hawaii ........................... 139.0

Idaho ........................... *

Illinois ........................... 155.0

Indiana .......................... 157.6

Iowa ............................ 158.8

Kansas .......................... 118.8

Kentucky ......................... 64.4

Louisiana ......................... 84.6

Maine ........................... 72.4

Maryland ......................... 123.5

Massachusetts ...................... 215.9

Michigan ......................... 128.0

Minnesota ........................ 149.1

Mississippi ........................ 61.5

*Figure does not meet standards of reliability or precision.

Table 5. Number and percent distribution of triplet and other higher order multiple births and singleton births by period of gestation and

race of mother: United States, 1992–94 total

Period of gestation2

All races1 White Black

Triplets3 Singletons Triplets3 Singletons Triplets3 Singletons

Number

Live births.................. 12,645 11,716,495 11,319 9,237,688 1,046 1,912,339

Percent distribution

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

Under 28 weeks .............. 13.4 0.6 12.7 0.4 22.4 1.6

28–31 weeks ................ 21.4 1.0 21.7 0.8 19.7 2.3

32–33 weeks ................ 21.8 1.2 22.0 1.0 18.9 2.5

34–36 weeks ................ 34.6 6.9 35.3 6.1 27.1 10.7

37–41 weeks . . . . . . . . . . . . . . . . 8.4 80.3 8.0 81.6 10.6 73.7

42 or more weeks . . . . . . . . . . . . . 0.5 9.9 0.4 10.1 1.3 9.2

Under 37 weeks .............. 91.1 9.8 91.6 8.3 88.2 17.1

Mean weeks ................ 32.2 39.1 32.2 39.2 31.4 38.4

1Includes races other than white and black.

2Period of gestation is in completed weeks of gestation.

3Includes births in quadruplet, and quintuplet and other higher order multiple deliveries.

Missouri ........................... 79.1

Montana ........................... *

Nebraska .......................... 149.0

Nevada ........................... 87.4

New Hampshire ...................... 178.4

New Jersey ......................... 165.6

New Mexico ........................ 70.8

New York . . . . . . . . . . . . . . . . . . . . . . . . . . 131.5

North Carolina ....................... 97.8

North Dakota ........................ 138.0

Ohio ............................. 140.9

Oklahoma .......................... 55.9

Oregon ........................... 90.1

Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . 111.7

South Carolina ....................... 108.6

Rhode Island ........................ 107.3

South Dakota ....................... 89.9

Tennessee ......................... 88.3

Texas ............................ 73.3

Utah ............................. 81.7

Vermont ........................... 84.2

Virginia ........................... 86.4

Washington ......................... 68.0

West Virginia ........................ 93.4

Wisconsin .......................... 106.9

Wyoming .......................... *

17
Table 6. Number of triplet and other higher order multiple births and singleton births by period of gestation and percent distribution by

birthweight according to period of gestation and race of mother: United States, 1992–94 total

Period of gestation and birthweight

All races1 White Black

Triplets2 Singletons Triplets2 Singletons Triplets2 Singletons

All gestations Number

Live births3,4 ....................... 12,645 1,171,695 11,319 9,237,688 1,046 1,912,339

Percent distribution

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

Less than 500 grams . . . . . . . . . . . . . . . . . . 3.4 0.1 3.2 0.1 6.1 0.3

500–999 grams. . . . . . . . . . . . . . . . . . . . . . 11.6 0.4 11.0 0.3 19.2 1.1

1,000–1,499 grams ................... 20.0 0.5 20.0 0.4 20.0 1.1

1,500–1,999 grams ................... 31.1 1.1 31.1 0.8 28.9 2.1

2,000–2,499 grams ................... 26.1 3.9 26.7 3.2 19.3 7.1

2,500–2,999 grams . . . . . . . . . . . . . . . . . . . 6.7 15.9 6.9 14.1 4.8 23.4

3,000–3,499 grams . . . . . . . . . . . . . . . . . . . 0.9 37.4 0.9 36.9 1.1 38.6

3,500–3,999 grams . . . . . . . . . . . . . . . . . . . 0.2 29.9 0.2 32.0 * 20.8

4,000 grams or more .................. * 10.8 * 12.1 * 5.4

Less than 1,500 grams ................. 35.0 1.1 34.1 0.8 45.4 2.5

Less than 2,500 grams ................. 92.1 6.0 92.0 4.8 93.6 11.7

Mean birthweight..................... 1,698 3,358 1,712 3,409 1,537 3,132

Less than 28 weeks Number

Live births3,4 ....................... 1,673 70,448 1,421 37,195 231 30,999

Percent distribution

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

Less than 500 grams .................. 24.6 17.4 24.5 16.5 25.7 18.5

500–999 grams...................... 60.1 53.6 60.0 55.2 61.9 51.8

1,000–1,499 grams ................... 12.8 14.9 13.4 15.6 * 14.1

1,500–1,999 grams . . . . . . . . . . . . . . . . . . . 1.7 4.7 1.6 4.1 * 5.3

2,000–2,499 grams . . . . . . . . . . . . . . . . . . . * 3.7 * 3.1 * 4.2

2,500–2,999 grams . . . . . . . . . . . . . . . . . . . * 5.8 * 5.4 * 6.1

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

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

4,000 grams or more .................. * * * * * *

Less than 1,500 grams ................. 97.5 85.9 97.9 87.3 96.0 84.4

Less than 2,500 grams ................. 99.8 94.2 99.9 94.6 99.6 93.9

Mean birthweight. . . . . . . . . . . . . . . . . . . . . 731 961 730 947 720 973

28–36 weeks Number

Live births3,4 ....................... 9,733 1,069,436 8,847 724,182 677 293,243

Percent distribution

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

Less than 500 grams . . . . . . . . . . . . . . . . . . * 0.0 * 0.0 * 0.1

500–999 grams. . . . . . . . . . . . . . . . . . . . . . 4.5 1.1 4.2 1.0 8.3 1.4

1,000–1,499 grams ................... 22.5 4.3 22.2 3.9 25.6 5.5

1,500–1,999 grams ................... 37.3 8.9 37.1 8.3 38.6 10.7

2,000–2,499 grams ................... 29.0 19.1 29.6 18.3 22.7 21.2

2,500–2,999 grams . . . . . . . . . . . . . . . . . . . 6.0 28.7 6.2 28.7 3.8 28.6

3,000–3,499 grams . . . . . . . . . . . . . . . . . . . 0.5 24.7 0.5 25.3 * 22.8

3,500–3,999 grams ................... * 10.6 0.1 11.5 * 8.1

4,000 grams or more . . . . . . . . . . . . . . . . . . * 2.6 * 3.0 * 1.6

Less than 1,500 grams ................. 27.1 5.4 26.5 4.9 34.1 7.0

Less than 2,500 grams ................. 93.4 33.4 93.2 31.5 95.4 38.9

Mean birthweight..................... 1,801 2,749 1,810 2,786 1,698 2,646

See footnotes at end of table.

18
Table 6. Number of triplet and other higher order multiple births and singleton births by period of gestation and percent distribution by

birthweight according to period of gestation and race of mother: United States, 1992–94 total—Con.

Period of gestation and birthweight

All races1 White Black

Triplets2 Singletons Triplets2 Singletons Triplets2 Singletons

37–47 weeks Number

Live births3,4 ....................... 1,108 10,467,811 946 8,394,930 122 1,570,294

Percent distribution

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

Less than 500 grams .................. * * * * * *

500–999 grams. . . . . . . . . . . . . . . . . . . . . . 2.3 0.0 2.4 0.0 * 0.0

1,000–1,499 grams . . . . . . . . . . . . . . . . . . . 9.3 0.0 9.1 0.0 * 0.1

1,500–1,999 grams ................... 19.4 0.2 18.7 0.2 25.4 0.5

2,000–2,499 grams ................... 38.1 2.3 38.6 1.9 32.8 4.5

2,500–2,999 grams ................... 22.2 14.7 22.8 12.9 18.0 22.8

3,000–3,499 grams . . . . . . . . . . . . . . . . . . . 6.0 39.0 6.1 38.1 * 42.3

3,500–3,999 grams ................... * 32.0 * 33.9 * 23.5

4,000 grams or more . . . . . . . . . . . . . . . . . . * 11.7 * 13.0 * 6.3

Less than 1,500 grams ................. 12.0 0.0 11.8 0.0 * 0.1

Less than 2,500 grams ................. 69.5 2.6 69.1 2.1 72.1 5.1

Mean birthweight..................... 2,223 3,437 2,231 3,475 2,158 3,266

* Figure does not meet standards of reliability or precision.

0.0 Quantity more than 0 but less than 0.5.

1Includes races other than white and black.

2Includes births in quadruplet and quintuplet and other higher order multiple deliveries.

3Includes births with period of gestation not stated.

4Includes births with birthweight not stated.

Table 7. Infant mortality rates for triplet and other higher order multiple births and singleton births by race of mother:

United States, 1983–91 birth cohorts

[Rates are per 1,000 live births in specified group]

Year

All races1 White Black

Triplets2 Singletons Triplets2 Singletons Triplets2 Singletons

1991 ........................... 93.7 7.8 79.1 6.4 209.2 15.1

1990 ........................... 102.4 8.0 100.8 6.6 134.0 15.4

1989 ........................... 101.5 8.7 97.1 7.1 160.3 16.2

1988 ........................... 112.8 8.7 108.9 7.3 139.9 16.2

1987 ........................... 136.0 8.9 130.9 7.4 157.7 16.3

1986 ........................... 113.6 9.2 123.2 7.7 45.7 16.7

1985 ........................... 159.7 9.5 138.9 8.0 302.5 17.0

1984 ........................... 125.9 10.4 119.1 8.8 156.4 17.9

1983 ........................... 156.1 10.9 148.5 9.3 215.7 19.0

1Includes races other than white and black.

2Includes births in quadruplet and quintuplet and other higher order deliveries.

19
Table 8. Infant mortality rates for triplet and other higher order multiple births and for singleton births by birthweight: United States,

birth cohorts 1987–91 total

[Rates are per 1,000 live births in specified group]

Birthweight Triplets1 Singletons Percent difference

499 grams or less .................................. 934.1 882.0 5.9

500–999 grams .................................... 449.2 451.5 –0.5

1,000–1,499 grams.................................. 47.4 112.7 –57.9

1,500–1,999 grams.................................. 15.2 50.4 –69.8

2,000–2,499 grams. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 19.0 –61.6

2,500 or more grams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * 3.7 *

*Figure does not meet standards of reliability or precision.

1Includes births in quadruplet and quintuplet and other higher order multiple deliveries.

Table 9. Infant mortality rates for triplet and other higher order multiple births and for singleton births by period of gestation: United

States, birth cohorts 1987–91 total

[Rates are per 1,000 live births in specified group]

Period of gestation1 Triplets2 Singletons Percent difference

Under 28 weeks ................................... 628.8 402.1 56.4

28–31 weeks ..................................... 64.8 66.9 –3.1

32–33 weeks ..................................... 17.9 26.8 –33.2

34–36 weeks ..................................... 12.7 11.9 6.7

37 weeks or more .................................. 21.5 4.0 437.5

1Completed weeks of gestation.

2Includes births in quaduplet and quintuplet and other higher order multiple deliveries.

Table 10. Infant mortality rates for the 5 leading causes of death for triplet and other higher order multiple births and singleton births:

United States, birth cohorts 1987–91 total

[Rates are per 100,000 live births in specified group]

Cause of death

Triplets1 Singletons

Rank Rate Rank Rate

Newborn affected by maternal complications of pregnancy ............ (761) 1 2,810.2 5 17.2

Respiratory distress syndrome ............................. (769) 2 1,824.8 4 60.2

Disorders relating to short gestation and unspecified low birthweight ...... (765) 3 729.9 3 84.2

Congenital anomalies ................................ (740–759) 4 700.7 1 189.0

Sudden infant death syndrome ............................ (798.0) 5 255.5 2 129.4

1Includes births in quadruplet and quintuplet and other higher order multiple deliveries.

20
Vital and Health Statistics

series descriptions

SERIES 1. Programs and Collection Procedures—These reports

describe the data collection programs of the National Center

for Health Statistics. They include descriptions of the methods

used to collect and process the data, definitions, and other

material necessary for understanding the data.

SERIES 2. Data Evaluation and Methods Research—These reports

are studies of new statistical methods and include analytical

techniques, objective evaluations of reliability of collected

data, and contributions to statistical theory. These studies also

include experimental tests of new survey methods and

comparisons of U.S. methodology with those of other

countries.

SERIES 3. Analytical and Epidemiological Studies—These reports

present analytical or interpretive studies based on vital and

health statistics. These reports carry the analyses further than

the expository types of reports in the other series.

SERIES 4. Documents and Committee Reports—These are 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. International Vital and Health Statistics Reports—These

reports are analytical or descriptive reports that compare U.S.

vital and health statistics with those of other countries or

present other international data of relevance to the health

statistics system of the United States.

SERIES 6. Cognition and Survey Measurement—These reports are

from the National Laboratory for Collaborative Research in

Cognition and Survey Measurement. They use methods of

cognitive science to design, evaluate, and test survey

instruments.

SERIES 10. Data From the National Health Interview Survey—These

reports contain statistics on illness; unintentional injuries;

disability; use of hospital, medical, and other health services;

and a wide range of special current health topics covering

many aspects of health behaviors, health status, and health

care utilization. They are based on data collected in a

continuing national household interview survey.

SERIES 11. Data From the National Health Examination Survey, the

National Health and Nutrition Examination Surveys, and

the Hispanic Health and Nutrition Examination Survey—

Data from direct examination, testing, and measurement on

representative samples of the civilian noninstitutionalized

population provide the basis for (1) medically defined total

prevalence of specific diseases or conditions in the United

States and the distributions of the population with respect to

physical, physiological, and psychological characteristics, and

(2) analyses of trends and relationships among various

measurements and between survey periods.

SERIES 12. Data From the Institutionalized Population Surveys—

Discontinued in 1975. Reports from these surveys are

included in Series 13.

SERIES 13. Data From the National Health Care Survey—These

reports contain statistics on health resources and the public’s

use of health care resources including ambulatory, hospital,

and long-term care services based on data collected directly

from health care providers and provider records.

SERIES 14. Data on Health Resources: Manpower and Facilities—

Discontinued in 1990. Reports on the numbers, geographic

distribution, and characteristics of health resources are now

included in Series 13.

SERIES 15. Data From Special Surveys—These reports contain

statistics on health and health-related topics collected in

special surveys that are not part of the continuing data

systems of the National Center for Health Statistics.

SERIES 16. Compilations of Advance Data From Vital and Health

Statistics—Advance Data Reports provide early release of

information from the National Center for Health Statistics’

health and demographic surveys. They are compiled in the

order in which they are published. Some of these releases

may be followed by detailed reports in Series 10–13.

SERIES 20. Data on Mortality—These reports contain statistics on

mortality that are not included in regular, annual, or monthly

reports. Special analyses by cause of death, age, other

demographic variables, and geographic and trend analyses

are included.

SERIES 21. Data on Natality, Marriage, and Divorce—These reports

contain statistics on natality, marriage, and divorce that are

not included in regular, annual, or monthly reports. Special

analyses by health and demographic variables and

geographic and trend analyses are included.

SERIES 22. Data From the National Mortality and Natality Surveys—

Discontinued in 1975. Reports from these sample surveys,

based on vital records, are now published in Series 20 or 21.

SERIES 23. Data From the National Survey of Family Growth—

These reports contain statistics on factors that affect birth

rates, including contraception, infertility, cohabitation,

marriage, divorce, and remarriage; adoption; use of medical

care for family planning and infertility; and related maternal

and infant health topics. These statistics are based on

national surveys of women of childbearing age.

SERIES 24. Compilations of Data on Natality, Mortality, Marriage,

Divorce, and Induced Terminations of Pregnancy—

These include advance reports of births, deaths, marriages,

and divorces based on final data from the National Vital

Statistics System that were published as supplements to the

Monthly Vital Statistics Report (MVSR). These reports provide

highlights and summaries of detailed data subsequently

published in Vital Statistics of the United States. Other

supplements to the MVSR published here provide selected

findings based on final data from the National Vital Statistics

System and may be followed by detailed reports in Series 20

or 21.

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

in these series, contact:

Data Dissemination Branch

National Center for Health Statistics

Centers for Disease Control and Prevention

Public Health Service

6525 Belcrest Road, Room 1064

Hyattsville, MD 20782

(301) 436–8500

E-mail: nchsquery@nch10a.em.cdc.gov

Internet: http://www.cdc.gov/nchswww/nchshome.htm
DHHS Publication No. (PHS) 97-1933, Series 21, No. 55

7-0100 (1/97)

COVER 4

PRINTER

PRINTER:

POSITIVE ART FOR BACK COVER (cover 4): PRINT SOLID PMS

NEGATIVE ART FOR FRONT COVER (cover 1): PRINT SOLID PMS