Maternal Weight 

Gain and the 

Outcome of 

Pregnancy 

United States, 1980 

An analysis of maternal weight gain during 

pregnancy by demographic characteristics 

of mothers and its association with birth 

weight and the risk of fetal death. 

Data From the National Vial Statistics 

System 

Series 21, No. 44 

\ 

DHHS Publication No. (PHS) 86-l 922 

U.S. Department of Health and Human 

Services 

Public Health Service 

National Center for Health Statistics 

Hyattsville, Md. 

June 1986 
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 

National Center for Health Statistics, S. Taffel, Maternal weight gain 

and the outcome of pregnancy, United States, 1980. Vita/ and Hea/th 

.Waristics. Series 21, No. 44. DHHS Pub, No. (PHS) 86–1922. Public 

Health Service. Washington. U.S. Government Printing Office, June 

1986. 

Library of Congress cataloging-in-publication data 

Taffel, Selma. 

Maternal weight gain and the outcome of pregnancy, 

United States, 1980, 

(Series 21, Data from the national vital statistics 

system ; no. 44) (DHHS publication ; no, (PHS) 86–1 922) 

DHHS publication ; no, (PHS) 86–1 922. 

Bibliography p. 

1. Pregnant women—United States—Weight gain— 

Statistic. 2. Birth weight, Low—united States— 

Statistic, 3. Birth wejght— Unite,cj States-Statistics. 

4. Pregnancy, Complications of—United States—Statistics,


5. Health surveys-United States. 6. United States—


Statistics, Medical. 1. National Center for Health


Statistics (U. S.) Il. Title. Ill, Series: Vital and


health statistic. Series 21, Data from the national


vital statistics system ; no. 44, IV. Series: DHHS


publication ; no. (PHS) 86-1922. [DNLM: 1, Birth Weight—


United States—statistics. 2, Body Weight—United States


—statistics. 3. Fetal Death—United States—statistics,


4. Pregnancy—United States—statistics.


W2 A N148VU no.44] 

HA21 1.A3 no. 44 304.6’3’0973021 S 86–60001 2 

[RG530.3.U5] [304.6’3’0973021] 

— 
National Center for Health Statistics 

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

Robert A. Israel, Deputy Director 

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

and Epidemiology 

Garrie J. Losee, Associate Director for Data Processing 

and Services 

Alvan O. Zarate, Ph.D., Assistant Director for International 

Statistics 

Peter L. Hurley, Acting Associate Director for Interview 

. and Examination Statistics 

Stephen E. Nieberding, Associate Director for Management 

Gail F. Fisher, Ph. D., Associate Director for Program 

Planning, Evaluation, and Coordination 

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

and Methodology 

Peter L. Hurley, Associate Director for Vital and Health 

Care Statistics 

Alice Haywood, Information Oflcer 

Vital and Health Care Statistics Program 

Peter L. Hurley; Associate Director 

Gloria Kapantais, Assistant to the Director for Data Policy, 

Planning, and Analysis 

Division of Vital Statistics 

:John E. Patterson, Director 

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

Robert L. Heuser, M. A., Chief Natality Statistics Branch 

Joseph D. Farrell, Chief Computer Applications Stafl 

Mabel G. Smith, ChieJ Statistical Resources Branch 
.

Contents 

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

Summary offindings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Weightgainduringpregnancy.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Race of mother . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Prepregnancyweight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smokinghabit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Socioeconomic status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Age ofmother . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Live-birth order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Marital status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . . . . . 

Outcome ofpregnancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Birthweight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Risk of fetal death . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .’. . . . . . . . . . . . . . . . . . . 

Appendix. Technicalnotes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Sources ofdata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Definitionofterms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Sampling error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Testingdifferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsamplingerror . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

List of text figures 

1.	 Percentofmothers gaininglessthan 16 poundsandpercentgaining26pounds ormoreduringpregnancybyprepregnancy 

weighti United States, 1980National Natality Sumey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

2.	 Percentofmothersgaininglessthan 16 pounds andpercentgaining26 pounds ormoreduringpregnancybyeducational 

attainmentofmothec United States, 1980NationalNatality Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

3.	 Percent oflive-bom infants oflow birth weight by matemal weight gain during pregnancy, according tomothe~s pre 

pregnancy weighC United States, 1980 NationalNatality Suwey. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

4.	 Mean birth weight oflive birthsto married mothers by weight gain during pregnancy, weight-for-height index, and 

smoklnghablt United States, 1980 NationalNatality Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . 

5.	 Fetal death ratios by weight gain during pregnancy and period of gestation United States, 1980 National Natality and 

Fetal Mortality Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

List of text tables 

A. Number of live births and percent distribution by weight gain during pregnancy and mean weight gain, according to race 

ofmother andperiod ofgestation United States, 1980 National Natality Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

B. Number oflivebirths rmdpercentdistnbution byweight gain during pregnancyandmean weightgain, according torace 

and prepregnancy weight of mothe~ United States, 1980 National Natality Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

c.	 Numberoflivebirths tomarriedmothers andpercentdistribution byweightgainduring pregnancyandmean weightgain, 

according to selectedmatemal characteristicx United States, 1980 National Natality Survey . . . . . . . . . . . . . . . . . . . . . . 

D,	 Number of live births and percent distribution by weight gain during pregnancy and mean weight gain, according to 

selected matemal characteristics United States, 1980 National Natality Survey. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

1 

2 

,3 

3 

4 

5 

5 

6 

6 

6 

9 

9 

14 

20 

21 

21 

21 

22 

23 

25 

5 

8 

12 

15 

17 

3 

4 

6 

7 

... 

Ill 
.

E. 

F. 

G. 

H. 

J. 

K. 

L. 

M< 

N. 

o. 

P. 

Q. 

R 

Number of live births, percent distribution by birth weight, and mean birth weight, according to weight gain during pregnancyand race ofmothec United States, 1980 National Natality Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Mean birth weight of live births by weight gain during pregnancy, race of mother, and period of gestation: United States, 

1980 National Natality Survey. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Percentoflive births weighingless than 2,500 grams byweight gainduringpregnancy, raceofmother, and prepregnancy 

weightofmothec United States, 1980 NationalNatality Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Percent of live births weighing less than 2,500 grams by weight gain during pregnancy and age of mothec United States, 

1980 National Natality Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Percent of live births weighing less than 2,500 grams by weight gain during pregnancy, age, and educational attainment of 

mothec United States, 1980 Nationa1 Natality Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Mean birth weight of live births to married mothers by weight gain during pregnancy, period of gestation, and smoking 

habit ofmother: United States, 1980 National Natality Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Mean birth weight of live births to married mothers by weight gain during pregnancy, weight-for-height index, and 

smoking habit ofmothec United States, 1980 National Natality Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Fetal death ratios by weight gain during pregnancy and period of gestation United States, 1980 National Natality and 

Fetal Mortality Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Fetal death ratios by weight gain during pregnancy, prepregnancy weight, and race of mothe~ United States, 1980 National Natality and Fetal Mortality Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Fetal death ratios by weight gain during pregnancy and age of mothec United States, 1980 National Natality and Fetal 

Mortality Survey s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 

Fetal death ratios by weight gain during pregnancy, period of gestation, and educational attainment of mothe~ United 

States, 1980 National Natality and Fetal Mortality Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Fetal death ratios by weight gain during pregnancy, period of gestation, and smoking habit of married mothers: United 

States, 1980 National Natality and Fetal Mortality Survey s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Fetal death ratios by weight gain during pregnancy, weight-for-height index, and smoking habit of married mothers: 

United States, 1980 National Natality and Fetal Mortality Surveys . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . 

10 

11 

11 

12 

13 

13 

14 

16 

18 

18 

19 

19 

19 

22 

23 

24 

25 

25 

List of appendix tables 

I.	 Standard errors for estimated mean birth weight of live births by weight gain during pregnancy, period of gestation, and 

race ofmothe~ United States, 1980 National Natality Suwey. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

II.	 Standard errors for estimated mean birth weight of live births to married mothers by weight gain during pregnancy, period 

of gestation, weight-for-height index, and smoking habiti United States, 1980 National Natality Survey. . . . . . . . . . . . . . 

III. Number of live births by selected characteristics: United States, 1980 National Natality Survey . . . . . . . . . . . . . . . . . . . . 

IV. Number of live births to married mothers by selected characteristics: United States, 1980 National Natality Survey . . . 

v. Parameters used to compute relative standard errors for live births and fetal deaths by maternal characteristic. . . . . . . . . 

Symbols 

. . . Data not available 

. . . Category not applicable 

Quantity zero 

0.0	 Quantity more than zero but less than 

0.05 

z	 Quantity more than zero but less than 

500 where numbers are rounded to 

thousands 

* Figure does not meet standards of 

reliability or precision (25 percent or 

more relative standard error) 
Maternal Weight Gain and 

the Outcome of Pregnancy 

by Selma M. Taffel, Division of Vital Statistics 

Introduction 

For several decades prior to the early 1970’s, common 

medlcrd practice in the United States was to minimize a mother’s 

weight gain during pregnancy in the belief that excessive gain 

might predispose her to the development of toxemia as well as 

to other obstetrical problems. A total weight gain of 20 pounds 

or less was frequently recommended. During this time, however, it became apparent that severe dietary restriction during 

pregnancy resulted in an elevated risk of low birth weight and 

necrologic impairment of the infant.1-5 In 1970, the National 

Academy of Sciences concluded that” an average weight gain 

of 24 pounds (range of 20–25 pounds) is commensurate with a 

better than average course and outcome of pregnancy” and 

that there was no scientific justification for routinely limiting 

weight gain to less than this amount.6 

According to current obstetric guidelines issued in 1983, 

usual weight gain should be 22–27 pounds. Weight reduction 

during pregnancy is no longer advised, even for women with a 

high prepregnancy weight, because of potential adverse effects 

on fetal growth and development.’ 

Although the relationship between a mother’s weight gain 

during pregnancy and the outcome of pregnancy has been explored in numerous studies, none has been national in scope. 

The present study investigates this association using information obtained from the 1980 National Natality Survey (NNS) 

and the 1980 National Fetal Mortality Survey (NFMS) conducted by the National Center for Health Statistics. The NNS 

is based on a probability sample of all live births occurring in 

the United States in 1980. The NFMS is based on a probabdity 

sample of fetal deaths with a physician’s estimate of gestation 

of 28 weeks or more or delivery weight of 1,000 grams or more 

if the physician’s estimate was not reported. 

This study includes only women for whom information on 

prenatal care was available. Information about the mother and 

live birth or fetal death is derived from the live bti cerdflcate 

or fetal death report and from questionnaires mailed to the 

mother (if married), to her attendant at delivery, and to the 

hospital where the delivery occurred. Weight of the mother at 

the start of pregnancy and at delivery were requested from all 

sources, but preference has been given in this report to the 

information reported by hospitals or attendants: Values for 

missing information have been impute& and each birth and 

fetal death has been weighted to derive national estimates. A 

more detailed description of these sweys is included in the 

Technical notes. 

The first pat of this study describes differences in maternal . 

weight gain during pregnancy for live births according to the 

period of gestation (the time between the first day of the mother’s 

last normal menstrual period and the day of birth) and certain 

sociodemographic and health characteristics known to be associated with variation in pregnancy outcome. These are race, 

prepregnancy weight, smoking habit, family income, educational attainment, age, marital status, and live-birth order of 

the infant. An analysis of weight gain for Hispanic-origin 

women was not possible because of the small numbers of these 

women in the ~S and NFMS. 

The second part of the study investigates the relationship 

between weight gain and pregnancy outcome, while controlling 

for period of gestation and mother’s race, prepregnancy weight, 

age, education, and smoking habit. Pregnancy outcome is aasessed in terms of birth-weight distribution, mean birth weight 

incidence of low birth weight (less than 2,500 grams or 5 

pounds 8 ounces); and the risk of fetal death, as measured by 

the fetal death ratio (number of fetal deaths of 28 weeks’ or 

more gestation per 1,000 live births). 
Summary of findings 

Current obstetrical guidelines state that usual weight gain 

in a normal pregnancy should be 22–27 pounds. But in 1980, 

one out of five white mothers and one out of four black mothers 

whose pregnancy extended to at least 40 weeks gained less 

than 21 pounds. 

Overall, 23 percent of women giving birth in 1980 gained 

less than 21 pounds during their pregnancy, and 12 percent 

gained less than 16 pounds. Black mothers were 50 percent 

more likely than white mothers to gain less than 21 pounds (33 

percent compared with 22 percent), and they were twice as 

likely to gain less than 16 pounds (20 percent compared with 

11 percent). The average weight gain of white mothers was 

29.1 pounds, 2.3 pounds higher than that of black mothers. 

Large racial differences in weight gain persist even after taking 

into consideration the shorter gestational period of black births 

and variation in prepregnancy weight. 

Substantial disparities in weight gain are evident for many 

groups of mothers: Women who have a high prepregnancy 

weight, who smoke during pregnancy, who have a low family 

income, who are 35 years of age or older or in their teens, who 

have less than 9 years of schooling, who are having a fourth or 

higher order birth, or who are unmarried are all more likely to 

gain less than 16 pounds and less likely to gain 26 pounds or 

more during their pregnancy. 

A low weight gain during pregnancy is associated with a 

lower average birth weight and a higher risk of a low birth 

weight (less than 2,500 grams) or fetal death outcome. Mean 

birth weight rises with increased weight gain for all gestational 

periods. For gestations of 40 weeks or longer, mean birth weight 

was 290 grams (10 ounces) higher when the mother gained 36 

pounds or more than when she gained less than 16 pounds; for 

gestations of less than 37 weeks, the average birth weight was 

380 grams (13 ounces) higher for a comparable increase in 

weight gain. Mean birth weight also increases with added 

weight gain for babies of mothers who smoked during pregnancy 

as well as for nonsmoking mothers. The increase in birth weight 

is especially marked for babies born prematurely (less than 37 

weeks’ gestation) to mothers who smoked, for these babies, 

birth weight was 671 grams (1 pound 8 ounces) higher for 

weight gains of at least 36 pounds than for weight gains of less 

than 16 pounds. Birth weight also increases markedly with 

added weight gain for babies of small women who smoked 

during their pregnancy. 

For comparable maternal weight gain, the average birth 

weight of black babies is lower than that of white babies, and 

black babies are more likely to weigh less than 2,500 grams 

(5% pounds), and less likely to weigh at least 3,500 grams (7 

pounds 12 ounces). 

A low prepregnancy weight combined with a small weight 

gain is associated with a very high incidence of low birth weighti 

29 percent of the babies born to mothers weighing less than 

110 pounds at the start of pregnancy who gained less than 16 

pounds weighed less than 5?4 pounds. The incidence of low 

birth weight declines shaqly as weight gain rises, regardless of 

prepregnancy weight, and the disadvantage in birth weight for 

babies of small women is reduced substantially. 

Nearly one out of five teenage mothers who gained less 

than 16 pounds bore a low-birth-weight baby in 1980, but the 

incidence of low birth weight dropped by three-fourths, to 4.9 

percent, when weight gain increased to at least 36 pounds. 

Higher educational attainment is associated with a reduced 

risk of low birth weight. When women gain less than 16 poun’ds 

during their pregnancy, however, there is no significant difference in the risk of low birth weight between those with less than 

a high school education and those who completed college (15.0 

percent compared with 12.2 percent). For all levels of educational attainment, the incidence of low birth weight is significantly lower for weight gains of at least 21 pounds than for 

weight gains of less than 16 pounds. 

The risk of a fetal death outcome is also lowered with added 

weight gain, up to 35 pounds. For the gestational periods 32-40 

weeks, the risk of fetal death dropped by about half as weight 

gain increased from less than 16 to 26-35 pounds. 

Although fetal death ratios are higher for mothers with a 

high prepregnancy weight, the risk of a fetal death outcome 

declines as weight gain increases for these women as well as for 

women with lower prepregnancy weight. Large declines in the 

risk of fetal death with added weight gain are also evident for 

women of all ages, for all levels of educational attainment, and 

for women who smoke during pregnancy as well as those who 

do not, regardless of gestational period or maternal size. 

Numerous studies have identified groups of women who 

are at highest risk of bearing a low-birth-weight infant or of 

having their pregnancy end in a fetal death. It is apparent from 

this study that these high-risk groups are also generally the 

most likely to have a smaller weight gain during their pregnancy. It is also evident that higher weight gain during pregnancy is associated with a significantly lower incidence of an 

adverse outcome for these high-risk groups. 

2 

. . 
Weight gain during pregnancy 

The analysis of differences in maternal weight gain in this 

section is limited to live births because of the dksimilarity in 

weight gain between live births and fetal deaths. The period of 

gestation for fetal deaths is shorter on the average than that for 

live btis, resulting in a lower average weight gain. However, 

because of the far smaller number of fetal deaths than of live 

b-, final conclusions are not altered because of their omission. 

Race of mother 

In 1980, about 12 percent of mothers who had a live birth 

gained less than 16 pounds during their pregnancy, and an additional 11 percent gained 16-20 pounds. Thus, nearly onequarter of all mothers gained 20 pounds or less. Slightly more 

than onehalf of all mothers (52 percent) gained 21-35 pounds, 

and the remaining 25 percent gained 36 pounds or more. This 

weight gain distribution reflects mainly the experience of white 

mothers. Black mothers were nearly twice as likely. as white 

mothers to gainless than 16 pounds (20 percent-compared with 

11 percent) and were also less likely to gain at least, 36 pounds 

(21 percent of black mothers compared with 26 percent of white 

mothers). One-third of all black mothers gained no more than 

20 pounds (table A). 

As would be expected, total weight gain during pregnancy 

is highly related to the Iength of the gestational period. Weight 

gain averaged 21 pounds for gestational periods of less than 32 

weeks, compared with 31 pounds for gestational periods of 42 

weeks or longer (table A). .. 

Table A. Number of live birtha and percent distribution by weight gain during pragnancy and maan weight gain, according to race of mothar 

and period of gestation: United States, 1980 National Natality Suwey 

Weight gain during pregnancy 

Less Standakd 

than ?6 16-20 2 1–25 26-35 36 pounds error 

Race of mother and period of gestation Live births Total pounds pounds pounds pounds or more Mean, . of mean “ 

. Number in 

Percent distribution Pounds 

Allracesl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,581 100.0 12.0 11.4 17.1 a4. -“- I 24.8 28.7 0.2 

Under 32 weeks . . . . . . . . . . . . . . . . . . . . . . . . 64 100.0 37.5 19.4 16.2 16.5 10.3 20.9 1.1 

32-35 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . 164 100.0 22.0 15.3 15.8 32.4 14.6 24.8 0.4 

36 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 100.0 16.6 14.1 19.6 31.5 18.1 26.5 0.9 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . 1,238 100.0 12.6 11.9 18.1 36.0 21.4 27,9 0.3 

40 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 869 100.0 9.4 10.5 17.2 37.2 25.7 29.6 0.3 

41 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528 100.0 8.6 10.5 18.3 34.2 28.5 ‘ 30.1 0.3 

42 weeks and over . . . . . . . . . . . . . . . . . . . . . . 591 100.0 11.0 9.9 13.9 32.0 33.2- 30.5 0.4 

White . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,917 100.0 10.5 11.1 17.3 35.4 25.7 29.1 0.2 

Under 32 weeks . . . . . . . . . . . . . . . . . . . . . . . . 42 100.0 37.9 19.1 16.9 17.7 *8.4 19.9 1.1 

32-35 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . 113 100.0 20.0 14.4 15.6 34.5 15.5 25.4 0.6 

36 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 100.0 15.6 13.7 19.1 34.0 17.6 27.0 ‘1.1 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . 988 100.0 10.3 11.7 18.5 36.9 22.6 28.4 0.3 

40weaks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 720 100.0 8.5 10.3 17.4 37.5 26.3 29.9 0.3 

41 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455 100.0 8.0 10.8 17.5 35.1 28.5 30.0 ‘ 0.4 

42 weeks and over . . . . . . . . . . . . . . . . . . . . . . 501 100.0 10.6 9.3 14.6 31.9 33.7 30.5 0.3 

Black . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554 100.0 20.0 12.6 16.0 30.0 21.3 26.8 0..5 

Under 32weaks . . . . . . . . . . . . . . . . . . . . . . . . 21 100.0 37.3 *1 9.0 *1 5.1 “14.2 “14.4 22,9 1.6 

32-35 weaks . . . . . . . . . . . . . . . . . . . . . . . . . . 47 100.0 27.0 14.6 15.9 29.4 13.1 23.7 0.4 

36 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 100.0 “1 8.3 *1 7.0 *23.2 “20.9 *20.6 24.5 -2.0 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . 208 100.0 23.6 12.5 16.0 29.4 18.4 25.8 0.8 

40 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 100.0 16.0 11.0 16.4 35.0 21.6 27.4 0.7 

41 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 100.0 “11.4 *9.9 *21 .7 28.8 28.1 30.5 1.2 

42 weeks and over . . . . . . . . . . . . . . . . . . . . . . 74 100.0 “14.1 *1 3.4 �9.1 32.2 31.2 30.0 1.3 

llncludss racss other than white and black. 

3 
White mothers gained, on the average, 2.3 pounds more 

than black mothers (29. 1 pounds compared with 26.8 pounds). 

This higher weight gain is only partly explained by the one-half 

week longer median gestational period of white than of black 

babies (40.3 weeks compared with 39.7 weeks in 1980). For 

almost all gestational periods there is a consistent pattern of a 

greater likelihood of a weight gain of less than 16 pounds for 

black women, although differences are not always statistically 

significant. 

For gestational periods of 37-39 weeks, the period when 

more than one-third of all births occurred, white mothers gained 

about 2% pounds more than black mothers. This greater weight 

gain reflects the fact that black mothers were more than twice 

as likely as white mothers to gain less than 16 pounds (24 

percent compared with 10 percent), and the greater likelihood 

that white mothers would gain at least 26 pounds (60 percent 

compared with 48 percent). Weight gain was also 2% pounds 

greater for white than black mothers when gestational age was 

40 weeks—again reflecting a much higher proportion of black 

mothers gaining less than 16 pounds. For gestational periods of 

40 weeks or longer, one out of five white mothers and one out 

of four black mothers gained less than 21 pounds. 

Prepregnancy weight 

A mother’s weight at the start of pregnancy is known to 

have a strong bearing on how much a mother gains during 

pregnancy and on pregnancy outcomes A more meaningful 

measure of maternal size than prepregnancy weight is the relationship between her weight and height. Maternal height was 

requested only on the mother’s questionnaire, and, hence, a 

weight-for-height index could be derived only for married 

mothers. When analyzing data for all mothers, prepregnancy 

weight is used as a surrogate for this index. 

It is clear from the data in table B and figure 1 that women 

who weigh at least 150 pounds at the start of pregnancy are far 

more likely than smaller women to gain less than 16 pounds; 

18 percent of women weighing 150–169 pounds and 29 percent 

of women weighing 170 pounds or more gained this little, compared with only 8 to 10 percent of women weighing less than 

150 pounds. In addition, a weight gain of 26 pounds or more is 

more common among women weighing less than 150 pounds at 

the start of pregnancy than among those weighing 170 pounds 

or more. Women with the highest prepregnancy weights, 

those weighing at least 170 pounds, gained on the average 24.0 

pounds, 4 to 6 pounds less than women with lower prepregnancy 

weights. 

Also of note is that black mothers who start pregnancy 

weighing 110-149 pounds are more likely than white mothers 

of comparable prepregnancy weight to gain less than 16 pounds 

and they are also less apt to gain at least 26 pounds. Weight 

gain averaged 3 pounds less for black than for white mothers 

weighhg 110-149 pounds at the start of pregnancy. 

If maternal size is gauged by a woman’s weight for her 

height rather than by her weight alone, it is again apparent that 

there is a pattern of lower weight gain for larger wome~ 21 

percent of married women who had a high prepregnancy weight 

for their height gained less than 16 pounds, compared with only 

6 percent of the women whose weight for height was low and 8 

percent of the women whose weight for height was average. 

Table B. Numbar of live births and percant distribution by weight gain during pragnancy and mean weight gain, according to race and 

prepragnancy weight of mothec United Statea, 1980 National Netality Survey 

Weight gain during pregnancy 

Less Standard 

than 16 t 6-20 21-25 26-35 36 pounds error 

Race and prepregnancy weight of mother Live births Total pounds pounds pounds pounds or more Mean of mean 

Numberin 

thousands Percent distribution Pounds 

Allracesl, . . . . . . . . . . . . . . . . . . . 3,581 100.0 12.0 11.4 17.1 34.7 24,8 28.7 0.2 

Less than l 10 pounds . . . . . . . . . . . . . 478 100.0 8.0 11.6 20.0 38,7 21.6 28.8 0.3 

110-129 pounds . ., . . . . . . . . . . . . . . . 1,315 100,0 7,8 11,4 17,9 39,5 23.4 29.2 0.2 

130-149 pounds, , . ., ..,,,..,. . . 968 100.0 10,0 10.6 16.0 34.3 29.0 30.2 0.2 

150-169 pounds . . . . . . . . . . . . . . . . 441 100.0 18.4 11.3 15.3 27.3 27.6 27.9 0.5 

170pounds or more, , .,,...... 379 100,0 28.7 13.1 15,7 22,6 19,8 24.0 0.7 

White . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,917 100.0 10,5 11,1 17,3 35,4 25.7 29.1 0.2 

Less than l 10 pounds.,..,.,.. . . 372 100,0 7.7 12,1 19.6 37.7 22.8 29.1 0.4 

110–129 pounds . . . . . . . . . . . . . . . . . . . 1,094 100.0 6,5 10,8 18.0 40.1 24.4 29.7 0.3 

130–149 pounds . . . . . . . . . . . . . . . . . . . . . . . 791 100,0 7.8 10.1 16.9 35.3 29.8 30.7 0.3 

150-169 pounds . . . . . . . . . . . . . . . . . . . . 370 100.0 16.9 10.7 15.6 29.1 27,6 28.1 0,6 

170rJounds or more ., ..,,...,. . . . . . . 290 100.0 27,9 13.7 14,7 23,2 20.5 24.0 0,9 

Black . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554 1000 20,0 12.6 16.0 30.0 21.3 26.8 0.5 

Lesathan l 10 pounds, ..,.,.., . . . . . . . . . 73 100.0 8.5 10.1 25:2 37.8 18.4 27.9 1.0 

110-129 pounds . . . . . . . . . . . . . . . . . . . 178 100,0 16,4 13.8 15.2 36.0 18.6 26.9 0.7 

130-149 pounds, .,, ..,....,. . . . . . . . 154 100.0 21.1 13.0 12,2 29.2 24.5 27.4 0.8 

150–169 pounds . . . . . . . . . . . . . . . . . . . 63 100.0 24.9 “13,6 *1 3.4 18,5 29.5 27.8 1.6 

170pounds or more,.,,..,.,,.. . . . . . . . . . 85 100.0 31.8 *1O,9 18.7 20.7 17.8 24.0 0.9 

Ilncludes rsces other than white and black, 

4 
Weight gain less than 16 pounds 

Less than 110 pounds 

110-129 pounds 

130-149 pounds 

150-169 pounds 

~


.-m 170 pounds or more


$ 

~ 

c 

m 

c 

~ 

~ Less than 110 pounds 

k 

110-129 pounds 

130-149 pounds 

150-169 pounds 

170 pounds or more 

o 10 20 30 40 50 60 70 

Percent of mothers 

Figure 1. Percent of mothers gaining less than 16 pounds and percent gaining 26 pounds or more during pregnancy by prepregnancy waighk 

United States, 1980 National Natality Survay 

Women whose weightlheight index was higher than average 

gained about 4 pounds less than smaller women (table C). 

Smoking habfi 

Information on cigarette smoking during pregnancy was 

available only for married mothers. Mc+hers who smoked during 

pregnancy were more likely than nonsmoking mothers to gain 

less than 16 pounds (14 percent compared with 10 percent). 

About one in four mothers who smoked during their pregnancy 

gained less than 21 pounds compared with one in five nonsmoking mothers. This differential cannot be explained by a 

dissimilarity in gestational period, because the median gestational period for women who smoked was only 0.1 week shorter 

than that of nonsmoking mothers. 

These data are consistent with previous research that found 

that weight gain during pregnancy is lower for women who 

smoke than for those who do not.g That study also concluded 

that the difference in mean weight gain between smokers and 

nonsmokers could not be accounted for by differences in length 

of gestation or mother’s prepregnancy weight, age, marital 

status, or educational attainment. 

Socioeconomic status 

Family income was requested only on questionnaires sent 

to mothers, and hence data on inc,ome reflect only the economic 

status of married mothers. The average weight gain of married 

mothers with a family income of at least $30,000 was 29.7 

pounds, 1.4 pounds higher than when family income was less 

than $9,000 (28.3 pounds) (table C). 

The proportion of women gaining less than 16 pounds declined by nearly half (from 16 to 9 percent) as family income 

increased from less than $9,000 to $30,000. Also evident is a 

small increment in the proportion of mothers gaining at least 26 

pounds as family income rises, although differences between 

adjacent income groups are not always significant (table C). 

Family income was available only for married mothers 

~om the survey, but information on educational attainment of 

the mother, a commonly used measure of socioeconomic status, 

5 
Table C. Number of live births to married mothers and percent distribution by weight gain during pregnancy and meen weight gain, according 

to salected matarnel characteristics: United States, 1980 National Natelity Survey 

Weight gain during pregnancy 

Less Standard 

than 16 76-20 21-25 26-35 36 pounds error 

Selected maternal characteristic Live births Total pounds pounds pounds pounds or more Mean of mean 

Number in 

thousands Percent distribution Pounds 

All births . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,930 100.0 10.6 11.1 17.1 35.8 25.4 29.1 0.2 

Weight-for-height indexl 

Low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726 100.0 6.3 10.4 19.1 40.1 24.1 29.8 0.2 

Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,478 100.0 7.6 10.4 16.4 38.0 27.5 30.2 0.2 

High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726 100.0 21.0 13.3 16.4 26.9 22.4 26.1 0.4 

Smoking habit during pregnancy 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767 100.0 13.6 11.8 15.8 33<1 25.8 28.6 0.4 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,162 100.0 9.6 10.9 17.6 36.7 25.3 29.2 0.1 

Family income 

Under $9,000 . . . . . . . . . . . . . . . . . . . . . . . . . . 440 100.0 15.9 11.0 15.6 31.6 25.9 28.3 0.4 

$9,000–$14,999 . . . . . . . . . . . . . . . . . . . . . . 625 100.0 11.2 11.9 18.1 33.5 25.1 28.9 0.4 

$15,000-$ 20,999 . . . . . . . . . . . . . . . . . . . . . . 708 100.0 10.0 11.8 17,6 35.4 25.2 29.0 0.3 

$21,000-$ 29,999 . . . . . . . . . . . . . . . . . . . . . 718 100.0 

$30,000 and over . . . . . . . . . . . . . . . . . . . . . . . 440 100.0 

lLowis less than 25th percentile for study group, average is25thto 74th percentile, 

was available for both married and unmarried women horn the 

live birth certificate. 

The more years of schooling a mother has completed, the 

higher her weight gain is likely to be (table D). Women who 

had completed college gained on the average 5 pounds more 

than women with no more than a grade school education (29.7 

pounds compared with 24.9 pounds). The proportion of mothers 

gaining at least 26 pounds during pregnancy generally increased 

with added years of education (figure 2), concomitant with a 

decline in the proportion of mothers gaining less than 16 pounds 

or 16–20 pounds. A gain of less than 16 pounds was three 

times as common among mothers with less than 9 years of 

schooling (20 percent) as among mothers who had completed 

at least 16 years of schooling (6 percent). Likewise, the proportion of mothers gaining only 16-20 pounds was 75 percent 

higher for women with only a grade school education (17 percent) than for women who had completed college (10 percent). 

College graduates were far more likely than mothers who had 

only a grade school education to gain 26 pounds or more (66 

percent compared with 46 percent) (figure 2). 

Age of mother 

Mothers 35 years of age or older me more likely than 

younger women to gain less than 16 pounds during their pregnancy; 24 percent of these older women had this low a weight 

gain compared with 10-11 percent of mothers aged 20-34 

years and 14 percent of teenage mothers. The likelihood of a 

more adequate weight gain of at least 26 pounds tends to decline 

for women in the oldest years of childbearing. Only 48 percent 

of women 35 years or older gained this much compared with 

56 percent of teenage mothers and 61 percent of mothers in 

their twenties. The average weight gain of women 35 years 

6 

8.4 10.8 17.6 38.0 25,1 29,4 0.4 

9.0 9.5 15.3 40.1 26,0 29.7 0.2 

and high ia 75th percentile or higher. 

or older was 3-5 pounds less than that of younger mothers 

(table D). 

One explanation for the lower average weight gain of older 

women is that they are more likely than younger women are to 

start pregnancy weighing at least 150 pounds. As noted previously, women with this prepregnancy weight are far more 

likely than women weighing less to have a low weight gain. 

Teenage girls are also more likely than women 20-34 years 

of age to gain less than 16 pounds. Reports on the nutritive 

status of pregnant adolescents indicate that suboptimal food 

intake during pregnancy is common in this age group. 10 

Live-birth order 

Weight gain during pregnancy is likely to decline with each 

successive birth (table D). Women having their first child gained 

on the average 5.6 pounds more than women having a fourth or 

higher order birth (30.5 pounds compared with 24.9 pounds). 

A woman having a fourth or higher order birth was 2% times as 

likely to gainless than 16 pounds (23 percent of these mothers) 

as a woman having a frost child (9 percent~ conversely, weight 

gains of over 25 pounds were about 1!4 times as frequent for 

women having a first btih (65 percent) as for women having a 

fourth or higher order birth (46 percent). The lower weight gain 

for women having higher order births is probably related to the 

fact that these mothers start pregnancy weighing more on the 

average than other women. As previously noted, weight gain 

declines with increased prepregnancy weight. 

Marital status 

Proportionately fewer married (11 percent) than unmarried 

women (18 percent) gained less than 16 pounds, and a weight 
Tabla D. Number of Iiva births and parcent distribution by waight gain during pregnancy and mean weight gain, according to selected matemel 

characteristics United States, 1980 National Natality Survey 

Weight gain during pregnancy 

Less Standard 

than 16 16-20 2 1–25 26-35 36 pounds error 

Salected maternal characteristic Live births Total pounds pounds pounds pounds or more Mean of mean 

All births . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Years of school completed 

O-8 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

9-n years . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

13-15 years . . . . . . . . . . . . . . . . . . . . . . . . . . . 

16years or more. . . . . . . . . . . . . . . . . . . . . . . . 

Age 

.Under20 years . . . . . . . . . . . . . . . . . . . . . . . . . 

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

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

30-34 yesrs . . . . . . . . . . . . . . . . . . . . . . . . . . . 

35 years and over . . . . . . . . . . . . . . . . . . . . . . . 

Live-birth order 

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

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

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

Fourth child ormore . . . . . . . . . . . . . . . . . . . . . 

Marital status 

Married . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Unmarried, . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Number in 

thousands Percent distribution 

3,581 100.0 12.0 11.4 17.1 34.7 24.8 28.7 0.2 

158 100.0 20.4 17.0 16.4 27.7 18.6 24.9 0.5 

659 100.0 17.3 12.4 16.4 31.0 22.9 27.4 0.4 

1,579 100.0 11.8 11.0 16.8 33.7 26.7 29.2 0.3 

676 100.0 9.4 11.4 18.1 36.2 24.9 29.2 0.4 

509 100.0 6.4 9.7 18.0 42.6 23.3 29.7 0.3 

553 100.0 14.4 11.7 18.0 31.3 24.7 28.5 0.4 

1,215 100.0 11.5 10.7 16.3 34.3 27.3 29.6 0.3 

1,101 100.0 10.4 11.1 17.4 37.0 24.2 28.7 0.3 

557 100.0 10.6 12.5 18.2 35.9 22.8 28.2 0.3 

154 100.0 23.6 13.9 15.2 29.5 17.9 24.9 0.7 

1,550 100.0 9.3 9.7 15.7 35.8 29.6 30.5 0.3 

1,149 100.0 11.5 12.1 18.4 35.5 22.5 28.3 0.2 

541 100.0 13.9 13.6 18.0 34.2 20.3 27.0 0.5 

341 100.0 22.7 13.4 17.9 27.8 18.2 24.9 0.5 

2,930 100.0 10.6 11.1 17.1 35.8 25.4 29.1 0.2 

651 100.0 18.0 12.6 17.3 29.8 22.3 27.1 0.4 

gain of at least 26 pounds was more common among married of husband-wife households,l 1 because low family income is


women (table D). On the average, married mothers gained 2 associated with lower weight gain. Unmarried mothers are also


pounds more than unmarried mothers (29. 1 pounds compared more likely to be teenagers, another factor related to lower


with 27.1 pounds). These differences probably reflect in part weight gain.


the far lower family income of female-headed households than


., ,, 

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7 
Weight gain less than 16 pounds 

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12 years	 $m$~~$ 12 ...................................... ...................................... 

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13-15 years ‘RjwjkwR 9 >:.:.:.:.:.:.:.:.:.:.:.:. 

16years or more	P .

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I Weight gain 26 pounds or more 

0-8 years 46 

9–1 1 years 54 

12 years 

13-15 years 

16 years or more 66 

I I I I i I I i 

o 10 20 30 40 50 60 70 

Percent of mothers 

Figure 2. Percent of mothers gaining less than 16 pounds and percent gaining 26 pounds or more during pregnancy by educational attainment 

of mother: United States, 1980 National Natality Suwey 

8 
Outcome of pregnancy 

The birth weight of live-born infants and the risk of fetal 

loss, as measured by the fetal death ratio (number of fetal deaths 

of 28 weeks of gestation or more per 1,000 live births), are 

, both commonly used yardsticks of pregnancy outcome. 

The risk of a low-birth-weight outcome (less than 2,500 

grams or 5 pounds 8 ounces) for live births has been shown to 

be related to a number of maternal and infant characteristics, 

including early or late childbearing, frst and high birth orders, 

low educational attainrnen~ out-of-wedlock childbearing smoking during pregnancy, and black race. 12,13Likewise, a higher 

risk of fetal death is known to be associated with low educational 

attainmen4 out-of-wedlock childbearing, and black race. 14,15 

As indicated earlier, a low weight gain during pregnancy is also 

more prevalent for all of these characteristics except fwst bkth 

order. In this section, the relationship between maternal weight 

gain and the risk of an unfavorable pregnancy outcome is explored while controlling for period of gestation and mother’s 

race, age, prepregnancy weight, education, and smoking habit 

The percent low birth weight by weight gain for gestational 

periods of less than 40 weeks and for women who smoked during 

pregnancy did not meet standards of reliability because of the 

small number of such bds in the sample. AnaIysis of these 

variables, therefore, is in terms of mean b@h weight. For other 

characteristics, analysis is in terms of the risk of a low-birthweight outcome. 

Birth weight 

It is widely recognized that an infant’s birth weight is a 

major determinant of its potentiaJ for survival and Mure development. As indicated in table E, there is a dramatic shfi in the 

birth weight distribution of live bmhs as weight gain during 

pregnancy rises. The proportion of low birth weight babies dec~med from 13.9 percent, when weight gain was less than 16 

“pounds, to 6.1 percent for gains of 21–25 pounds, and to 4.0 

percent when mothers gained 36 pounds or more. The proportion of babies weighing 2,500-2,999 grams (5 pounds 9 ounces 

to 6 pounds 9 ounces) also dropped steeply with increases in 

weight gain, from 24.5 percent for weight gains of less than 16 

pounds to 10.2 percent for women gaining at least 36 pounds. 

Concomitantly, the likelihood of a baby weighing at least 3,500 

grams (7 pounds 12 ounces) more than doubled (from 24.8 to 

51.7 percent) as weight gain increased from less than 16 to 36 

pounds or more. This major shift in the bti weight distribution 

as weight gain increases is reflected in the mean birth weigh~ 

which was 435 grams higher (about 1 pound) for weight gains 

of 36 pounds or more than for weight gains of less than 16 

pounds (3,5 15 grams compared with 3,080 grams). Shnilar 

changes in birth weight distributions with increased weight gain 

are evident for both white and black babies. However, for a 

comparable weight gain, the mean birth weight of black babies 

is lower than that of white babies, and black babies are more 

likely to weigh less than 2,500 grams and are less likely to 

weigh 3,500 grams or more. 

Period of gestation 

Because weight gain and fetal size both increase as pregnancy progresses, it is essential to examine the relationship 

between weight gain and bti weight while controlling for length 

of the gestational period. The data in table F indicate that for 

all gestational periods, mean bti weight generally rises with 

increases in maternal weight gain. 

For gestations of less than 37 weeks, mean birth weight 

was 380 grams (13 ounces) higher for weight gains of 36 pounds 

or more than for weight gains of less than 16 pounds. The 

comparable difference in mean bti weight for gestations of 

37–39 weeks was 300 grams (11 ounces). For pregnancies 

extending to 40 weeks and beyond, there is still a noticeable 

difference in mean birth weight approximately 290 grams (10 

ounces), for the highest compared with the lowest weight gain 

categories. This same pattern is evident for white births and for 

black births of at least 37 weeks of gestation. 

Prepregnancy weight 

A woman’s prepregnancy weight and her weight gain during 

pregnancy are strongly related to the incidence of low birth 

weigh~ and prepregnancy weight interacts with weight gain to 

increase or lessen this risk. A low prepregnancy weight combined with a small weightgjain is associated with the highest 

incidence of low birth weight (table G). 

Regardless of a mother’s prepregnancy weight, there is a 

consistent pattern of declining risk of a low-birth-weight outcome as weight gain increases. This is especially noticeable for 

women weighing less than 110 pounds at the start of pregnancy, 

for whom a weight gain of less than 16 pounds was associated 

with an incidence of low birth weight of 28.8 percent more 

than three times the incidence when weight gain was 21–25 

pounds (8.7 percent) and five to six times the incidence when 

weight gain was 26 pounds or more (4.9–5.4 percent). For 

women weighing 110-129 pounds initially, the difference in 

incidence of low bti weight with increased weight gain is 

nearly as dramatic, dropping from 20.1 percent for a gain of 

9 
Table E. Number of Iiva births, parcent distribution by birth waight, and mean bitih waight, according to waight gain during pregnancy and 

race of mother: Unitad States, 1980 National Natality Survay , 

Weight gehr during pregnancy 

Less 

than 16 16-20 21-25 26-35 36 pounds 

Rece of mother and birth weight Total pounds pounds pounds pounds or more 

All racesl Number in thousands 

Liva births . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,581 428 408 613 1,242 889 

Percent distribution 

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

Lesathan 2,500 grams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 13.9 11.4 6.1 5.0 4.0 

2,500-2,999 grams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.1 24.5 19.6 18.1 15.2 10.2 

3,000-3,499 grams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37.3 36.8 42.2 38.6 37.5 34,1 

3,500 grams ormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39.9 24.8 26.8 37.2 42.3 51,7 

Mean in grams 

Birth waight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,343 3,080 3,175 3,315 3,381 3,515 

Standard error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 20 19 13 10 12 

White Number in thouaanda 

Liva births . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,917 306 323 505 1,034 750 

Parcent distribution 

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100.0 100.0 100.0 100.0 100.0 1Oc.o 

Less than 2,500 grams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 12.5 9.8 5.3 4.2 3.2 

2,500-2,999 grams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4 21.6 17.9 16.7 13.9 9.0 

3,000-3,499 grams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36.6 37.0 43.0 38.1 37.0 33.0 

3,500 grams ormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.2 28.9 29.3 39.8 44.9 54.8 

Mean in grams 

Birth weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,391 3,149 3,226 3,348 3,418 3,554 

Standard error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 25 22 15 11 13 

Black Number in thousanda 

Live births . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554 111 70 89 166 118 

Percent distribution 

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

Less than 2,500 grams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5 18.3 19.1 10.0 10.1 8,3 

2,500-2,999 grams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.6 32.4 27.6 26.0 22.1 17.8 

3,000 -3,499 grams, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39.0 36.2 35,7 40.4 41.4 38.9 

3,500 grams or more..........,.. . . . . . . . . . . . . . . . . . . . . 24.0 13,1 17,6 23.6 26.3 35.1 

Mean in grams 

Birth weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,099 2,879 2,950 3,137 3,156 3,284 

Standard error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 28 36 36 25 31 

‘Includes racas Otherthan white and black. 

less than 16 pounds to 7.5 percent for a gain of 21-25 pounds 

and to 3.6 percent when weight gain exceeded 35 pounds. 

This same pattern of a sharply lower incidence of low birth 

weight as weight gain increases, independent of prepregnancy 

weighg is evident for both white and black births. However, 

because of the small numbers of black women in the sample, 

estimates were generally not reliable or differences statistically 

significant for many categories. 

As shown in figure 3, there is a convergence in the risk of a 

low-birth-weight outcome from the lowest to the highest prepregnancy weight as weight gain increases. When weight gain 

was less than 16 pounds, the incidence of low birth weight for 

babies born to mothers weighing less than 110 pounds was 

28.8 percentj four times the incidence for mothers who weighed 

150 pounds or more initially (7.2 percent). But when weight 

gain was at least 26 pounds, there was no significant difference 

in the incidence of low birth weight between the lowest and 

highest prepregnancy weights. Apparently, the substantial disadvantage in birth weight for babies of women with a low prepregnancy weight is reduced considerably as weight gain increases. 

Age of mother 

It is well documented that teenage girls are more likely 

than other age groups to bear a low-birth-weight baby.12 But 

increased weight gain during pregnancy lowers this risk substantially. As shown in table H, nearly one out of five teenagers 

gaining less than 16 pounds (19.2 percent) gave birth to a baby 

10 
Table F. Mean birth weight of live births by weight gain during”pregnancy, race of mother, and period of gestation United Stetes, 1980 ,., National Netality Survay 

Weight gain during pregnancy 

Less 

than 16 16-20 21-25 26-35 36 pounds 

Rata of mother and per;od of gestation Total pounds pounds pounds pounds . or more .,. 

Grams 

Allracesl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,343 3,080 3,175 3,315 3,381 3,515 

Under 37 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,624 2,387 2,448 2,704 2,782 2,767 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,281 3,120 3,187 3,251 3,301 3,420 

40weeka and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,510 3,340 3,363 3.472 3,521 3,628 

White . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,391 3,149 3,226 3,348 3,418 ..>. .-.: 3,554

. ../[ 

Under 37 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,676 2,445 2,494 2,675 2.833 . ‘2,854 “ 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,321 3,178 3,215 3,286 3,330 . 3,454.. 

40 weeks and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,541 3,381 3,396 3,494 3,551 3,655 

Black . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,099 2,879 2,950 3,137 3,156 , 3,284, 

Under 37 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,472 2,223 2,293 2,760 2,613 .2,550 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,095 2,991 3.028 3,085 3,129 3,228 

40 weeks and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,330 3,176 3,218 3,336 3,319 3,475 

1Includes races other than white and black. ,, 

Table G. Percent of live births weighing less then 2,500 grams by weight gain during pregnancy, race of mother, and prepregnancy weight “ 

of mothec United Statas, 1980 National Netalii Survey . . . 

Weight gain during pregnancy 

Less .. . 

than 16 16-20 21-25 26-35 36 pounds 

Race and prepregnancy we!ght of mother Total pounds poun”ds pounds pounds or mora 

All races! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 13.9 11.4 6.1 5.0 4.0 

Less than 110 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5 28.8 20.5 8.7 . 4,9 5.4 

110-129 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 20.1 13.8 7.5 5.5 3.6 

130-149 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7 14.5 7.7 4.7 4.8 3.6 

150pounds ormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.0 7.2 6.4 3.4 3.9 4.3 

White . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 12.5 9.8 5.3 4.2 3.2 

Less than 110 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.9 24.9 19.0 8.2 5.2 4.6 

110-129 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 19.3 11.4 6.2 4.8 : 3.3 

130-149 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 13.9 6.5 3.8 3.4 2.7 

150pounds or more . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.0 6.0 5.6 3.6 2,6 3.2 

Black . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5 18.3 19.1 10.0 10.1 8.3 

Less than 110 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3 56.6 ‘30.7 “9.0 *4.9 “6.7 

110-129 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.0 22.8 27.7 16.4 10.1 *6.9 

130-149 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.0 15.9 *1 2.9 *11.8 14.0 9.9 

150pounds ormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 11.5 *9.3 *2.2 *8.9 *8.4 

llncludea races other than white and black. 

weighing less than 2,500 grams, but the incidence of low birth 

weight dropped to 7.4 percent when teenagers gained 2 1–25 

pounds, to 6.3 percent for gains of 26–35 pounds, and to a low 

of 4.9 percent for weight gains in excess of 35 pounds. 

As weight gain increases, the risk of a low-bti-weight 

outcome declines for other age groups as well. For women past 

the teenage years, the incidence of low birth weight was 11–13 

percent for weight gains of less than 16 pounds and fell to 4–5 

percent when weight gain exceeded 25 pounds (table H). 

Educational attainment 

A mother’s educational attainment and her f~ily income 

are both reliable indicators of her socioeconomic status. Family 

income was requested only of married mothers~ &e NNS, but 

years of schooling was available for married and unmarried 

mothers from live bti certificates. ., 

Previous studies of national and State data have found.that 

higher levels of educational attainment are associated with a 

sharply reduced incidence of low birth weight.12’lGThe proportion of Iow-bti-weight babies born to mothers im the INNS 

with 16 years or more of schooling (5.0 percent) was about half 

that of mothers with less than 12 years of schooling (9.3 per’ 

cent) (table J). But for women who had completed college, the 

incidence of low bhth weight averaged 12.2 percent when 

weight gain was less than 16 pounds and 8:5 percent when 

weight gain was 16–20 pounds. For women gainiig less thim 

“11

�

�

�

�

30 

20 

10 

9 

8 

7 

4 

Prepregnancy weight 

_ -Less than 110 pounda 

�_-110-129 pounds 

—130–149 pounds 

\ . . . ...150 pounds or more 

\ 

\ 

\ 

\ 

\ 

A*9. �. . �. . 

* 

* 

* 

� * .*** 

****. 

1~


Leas 16-20 21-25 26-35 36 

than pounds pounds pounds pounda 

16 or 

pounds more 

Weight gain 

NOTE Low biflhweight isdefined as bimhweight oflessthan2,5OO 

grams or5 pounds 8 ounces. 

Figure 3. Percent of live-born infants of low birth weight by 

maternal weight gain during pregnancy, according tomothar’a 

prepregnancy weight: United States, 1980 National Nataiity Survey 

16 pounds during pregnancy, the risk of a low-birth-weight 

outcome is not significantly different for those who had not 

completed high school than for those who had completed college 

(15.0 percent compared with 12.2 percent). 

For all levels of educational attainment, the incidence of 

low birth weight is significantly lower for weight gains of at 

least 21 pounds compsred with gains of less than 16 pounds. 

For women who had not completed high school (who were at 

highest risk of a low-birth-weight outcome), the incidence of 

low birth weight dropped from 15.0 percent for a gain of less 

than 16 pounds to 8.5 percent when weight gain was 21-25 

pounds and to 5.7 percent for gains of 36 pounds or more. 

Because teenage mothers have not had the opportunity to 

complete their education, the proportion of low-birth-weight 

babies by educational attainment is also shown for women 20 

years of age and over. The same pattern of a sharply reduced 

risk of low birth weight with added weight gain is also evident 

for these women (table J). 

Part of the reason for the higher incidence of low birth 

weight for women with less than a high school education is that 

they are far more likely to gain less than 16 pounds than those 

mothers with at least 12 years of schooling (table D). 

Smoking habit 

About one-quaker of the women giving birth in 1980 

smoked during their pregnancy. As noted previously, mothers 

who smoked gained less than nonsmoking mothers. The mean 

birth weight of babies of mothers who smoked was also lower, 

by 204 grams (7 ounces), than the mean birth weight of babies 

of mothers who were nonsmokers (3,236 grams compared with 

3,440 grams). But for smoking and nonsmoking mothers alike, 

mean birth weight rises significantly as weight gain increases 

from less than 16 to 21 pounds or higher (table K). 

The effect of increased weight gain for smoking and nonsmoking mothers was examined according to gestational period 

because this is so strongly related to birth weight and because a 

mother who smokes is more likely to have a preterm birth (less 

than 37 weeks’ gestation). For gestational periods of 37-39 

weeks and 40 weeks or longer, the babies of mothers who smoked 

weighed less than those of nonsmoking mothers by approximately 200 grams (7 ounces). For all gestational periods, mean 

birth weight increases with added weight gain, regardless of 

smoking habit. For mothers who smoked, the increase in birth 

weight is especially noticeable for preterm births; mean birth 

weight rose 671 grams (1 pound 8 ounces), from 2,212 grams 

.,. 

/’ 

Table H. Parcent of live births weighing less than 2,500 grams by weight gain during pregnancy and age of mothen United Statas, 1980 

National Natality Survey 

Weight gain during pregnancy 

Less 

than 16 16–20 2 1–25 26-35 36 pounds 

Age of mother Total pounds pounds pounds pounds or more 

Alleges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 13.9 11.4 6.1 5.0 4.0 

Under 20 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1 19.2 15.2 7,4 6,3 4.9 

20-24 years....,...,,..,.,.. . . . . . . . . . . . . . . . 6.8 13.4 11.6 7,4 4,9 3.9 

25-29 yeara . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8 11.2 9.4 5.2 4.8 3.8 

30yaars and over . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 13,2 10,9 4.6 4.3 3.6 

12 
Table J. Percent of live births weighing less than 2,500 grams by weight gain during pragnancy, age, and educational attainment of mothec 

United States, 1980 National Natality Survey 

Weight gain during pregnancy 

Less 

than 16 16-20 2 1–25 26-35 36 pounds 

Age of mother and years of school completed Total pounds pounds pounds pounds or more 

Alleges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 13.9 11.4 6.1 5.0 4.0 

O-n years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3 15.0 12.9 8.5 7.4 5.7 

12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 13.7 12.9 6.0 5.0 3.7 

13-15 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9 12.8 7.6 5.3 3.4 2.5 

16years or more . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.0 12.2 8.5 4.0 3.7 4.6 

20years ofage Gr over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 12.6 10.6 5.9 4.7 3.8 

O-n years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.8 12.4 12.0 8.1 7.5 5.7 

12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6 12.8 12.2 6.1 5.1 3.6 

13-15 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9 12.7 7.5 5.5 3.4 2.5 

16years or more . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.0 12.2 8.6 4.0 3.7 4.6 

Table K. Mean birth weight of live births to married mothers by waight gain during pregnancy, period of gestation, and smoking habit of 

mothen United Statas, 1980 National Natality Survey 

Period of gestation and smoking habit of mother 

Allgestational periods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Under 37 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

40 weeks and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Total 

3,387 

3,236 

3,440 

2,664 

2,553 

2,715 

3,314 

3,153 

3,370 

3,541 

3,414 

3,585 

Weight gain during pregnancy 

Less 

than 76 16-20 2 1–25 26-35 36 pounds 

pounds pounds pounds pounds or more 

Grams 

3.138 3,221 3,354 3,418 3,541 

3,037 3,106 3,173 3,266 3,402 

3,189 3,266 3,411 3,467 3,592 

2,407 2,458 2,695 2,825 2,828 

2,212 2,343 2,321 2,781 2,883 

2,505 2,504 2,826 2,846 2,798 

3,160 3,212 3,289 3,324 3,444 

3,046 3,059 3,163 3,157 3,269 

3,216 3,277 3,33T 3,375 3,501 

3,370 3,393 3,499 3,559 3,649 

3,308 3,320 3,329 3,428 3,518 

3,401 3,420 3,551 3,600 3,697 

weight gain was not as pronounced for the largest women who 

smoked, mean birth weight was still significantly higher, by 

261 grams (9 ounces), for a weight gain of 36 pounds or more ~ 

compared to weight gains of less than 16 pounds. This same 

pattern is also apparent for nonsmoking mothers. 

In a previous analysis of birth outcome for white mothers 

in the 1980 National Natal@ Survey,17 it was determined that 

of all factors considered only period of gestation had a stronger 

effect than weight gain on the risk of low birth weight. When 

differences in mother’s age and education, and live bti order, 

sex, and period of gestation of the child were accounted for, 

women gaining less than 21 pounds were found to be 2.3 times 

as likely to bear a low-birth-weight infant as women with a 

higher weight gain. A further analysis limited to married 

mothers, which included smoking habit as well, did not change 

this conclusion. It has been postulated that the lower level 

of birth weight associated with maternal smoking during pregnancy is partly due to the decreased weight gain of mothers 

who smoke.g The data presented in this study support this 

theory. 

to 2,883 grams, as weight gain increased from less than 16 to 

36 pounds or more. 

Because maternal” size is also strongly related to birth 

weight, the effect of increased weight gain for married mothers 

who smoked and for those who did not smoke was examined 

according to their prepregnancy weight for height (table L and 

figure 4). Regardless of maternal size or smoking habit, increased weight gain is associated with higher birth weight. 

The increase in birth weight with added weight gain is 

especially evident for smokmg women whose weight for their 

height was low or average at the start of pregnancy. The average 

birth weight of babies born to women with a low weight-forheight index who smoked was 683 grams (1 pound 8 ounces) 

higher for weight gains of 36 pounds or more than for weight 

gains of less than 16 pounds (3,314 grams compared with 2,631 

grams). For women of average size who smoked, the difference 

in mean birth weight for weight gains of less than 16 pounds 

compared with weight gains of 36 pounds or more was 480 

grams (1 pound 1 ounce), 

While the difference in mean birth weight with increased 
Table L. Mean birth weight of live births to married mothers by weight gein during pregnancy, weight-for-height index and smoting habit 

of mothec United States, 1980 National Natality Survey 

Weight gain during pregnancy 

Less 

than 16 16-20 27-25 26-35 36 pounds 

Weight-for-height index~ and smoking habit of mother Total pounds pounds pounds pounds or more 

Grams 

All mothers, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,387 3,138 3,221 3,354 3,418 3,541 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,236 3,037 3,106 3,173 3,266 3,402 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,440 3,189 3,266 3,411 3,467 3,592 

Low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,263 2,825 3,035 3,217 3,312 3,431 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,122 2,631 2,811 3>069 3,174 3,314 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,323. 2,927 3,100 3,276 3,374 3,483 

Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,399 3,035 3,181 3,365 3,432 3,555 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,228 2,918 3,065 3,135 3,292 3,398 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,453 3,097 3,231 3,428 3,471 3,606 

High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,487 3,307 3,432 3,490 3,537 3,626 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,379 3,258 3,365 3,379 3,384 3,519 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,526 3,330 3,458 3,526 3,581 3,665 

1Low is lass than 25th percentile for study group, average is 25th–74th percentile, and high is 75th percentile or higher. 

Risk of fetal death 

The weight gain of mothers whose pregnancy ended in a 

fetal death with a physician’s estimate of gestation of 28 weeks 

or more or delivery weight of at least 1,000 grams when the 

physician’s estimate was not reported (late fetal death) is available from the National Fetal Mortality Survey. By combming 

this information with the weight gain data for live births from 

the National Natality Survey it is possible to determine the risk 

of a fetal death outcome for specific weight gains. In this study, 

the risk of fetal death is measured by the fetal death ratio—the 

number of late fetal deaths per 1,000 live births. 

Period of gestation 

As noted earlier, a woman’s weight gain during pregnancy 

is strongly influenced by the length of the gestational period. 

More than one-fourth of all late fetal deaths occurred at less 

than 37 weeks of gestation. Therefore, in this discussion the 

relationship between weight gain during pregnancy and the risk 

of a fetal death outcome is examined by gestational period. 

As weight gain increases from less than 16 pounds to 26-

35 pounds, there is a general pattern of declining risk of fetal 

death for all gestational periods of 32 weeks or longer (table M 

and figure 5). For example, for the gestational period 37–39 

weeks, the fetal death ratio declined from 5.0 per 1,000 live 

births for weight gains of less tharr 16 pounds to 2.8 for weight 

gains of 26-35 pounds, a drop of 44 perter% for similar weight 

gains, the drop was 59 percent when period of gestation was 40 

weeks. However, weight gains of 36 pounds or more are generally associated with a slight rise in the risk of fetal death 

compared with weight gains of 26–35 pounds. 

Prepregnancy weight 

The risk of a fetal death outcome generally escalates with 

increases in the mother’s prepregnancy weight (table N), in 

contrast to the decline in incidence in low birth weight with 

greater prepregnancy weight. The fetal death ratio was nearly 

twice as high for a woman weighing 170 pounds or more at the 

start of pregnancy as for a woman weighing less than 110 

pounds initially (8.2 compared with 4,3). But regardless of the 

mother’s prepregnancy weight, the fetal death ratio declines 

sharply with increased maternal weight gain, up to 26–35 

pounds. This is especially evident for women with the lowest 

prepregnancy weights; among women weighiig less than 110 

pounds at the start of pregnancy, the fetal death ratio dropped 

from 11.6 for weight gains of less than 16 pounds to 2.8 for 

weight gains of 26-35 pounds. The comparable decline in the 

fetal death ratio was nearly as steep for women with a prepregnancy weight of 110-129 pounds, dropping from 11.2 to 3.3. 

Because black women start pregnancy weighhg more on 

the average than white women, fetal death ratios are shown by 

race. For both white and black mothers, the elevated risk of a 

fetal death outcome for women with a high prepregnancy weight 

is evident. For both racial groups, there is a consistent pattern 

of reduced risk as weight gain increases, although differences 

for several prepregnancy weight categories for black women 

are not significant and estimates are not reliable because of the 

small number of such sample cases. 

Age of mother 

For women of all ages, there is a pronounced and consistent decline in the fetal death ratio as weight gain increases 

from less than 16 pounds to 26–35 pounds. The decline was 

slightly more than 50 percent for teenagers (from 8.1 to 3.9) 

and between 64 and 67 percent for other ages (table O). 

Regardless of age, when weight gain is more than 35 

pounds, there is a slight, but not statistically significant, rise in 

the fetal death ratio relative to the ratio for gains of 26–35 

pounds. However, the fetal death ratios for this highest weight 

gain category were still at least 40 percent lower than the ratios 

for weight gains of less than 16 pounds. 

Educational attainment 

The risk of a fetal death outcome is 30 percent lower for 

women who had completed at least 13 years of schooling (4.3) 

than for women with less than a high school education (6.1) 

(table P). However, when weight gain is less than 21 pounds, 

14 
� .Srnoker 

Is Nonsmoker 

Less than 16 pounds 

z


.-m 16-20 pounds


:


5


E


.-m 21-25 pounds


$


3
 CJ


26-35 pounds 

36 pounds or more 

Less than 16 pounds 

E


.-m


2 16-20 pounds


&


z


.-0)
 21-25 pounds 

$ 

0 

a 

s

al 

z 26-35 pounds 

36 pounds or more 

Less than 16 pounds 

E


.-m 16-20 pounds


;


~“


z

0) 21-25 pounds
 .-


:


x


.-m


x 26-35 pounds


36 pounds or more 

o 2,500 2,800 3,100 3,400 3,700 

Mean birth weight in grams 

Figure 4. Mean birth weight of live births to married mothars by weight gain during pregnancy, weight-for-height indax, and smoking habk 

United States, 1980 National Natality Survey 
Table M, Fetal daeth ratios by waight gain during pregnancy and period of gestation: United States, 1980 National Natality and Fetal 

Mortality Survays 

[Ratios are late fetal deaths per 1,000 live births] 

Weight gain during pregnancy 

Less 

than 16 16-20 27-25 26-35 36 pounds 

Period of gestation Total pounds pounds pounds pounds or more 

Allgastational periods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 10.5 6.7 4.8 3.8 4.1 

Under 32 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46.8 52.8 48.1 40.9 47.1 “31 .7 

32–35 weeks, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4 30.7 25.3 25.3 15.6 18.8 

36 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7 18.3 15.4 10.8 9.7 12.5 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 5.0 3.5 3.4 2.8 3.1 

40 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 6.9 4.4 3.0 2.8 4.2 

41 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7 2.3 2.0 1.7 1.4 2.0 

42 weeks and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 4.4 3.3 3.0 3.1 3.1 

fetal death ratios are not sigrdicantly lower for better educated 

women. 

For all levels of educational attainment, added weight gain 

is associated with a sharp decline in the risk of fetal death. For 

women who had not completed high school, the fetal death 

ratio for women gaining 36 pounds or more (5.1) was about 

half that of women gaining less than 16 pounds (9.6~ for women 

who had completed at least one year of college, the fetal death 

ratio was tvothirds lower for women gaining 36 pounds (3.5) 

than for women gaining less than 16 pounds ( 10.9). 

The pattern of lower risk of fetal death with added weight 

gain is evident for preterm as well as full-term deliveries 

(table P). 

Smoking habit 

The risk of a fetal death outcome is higher for women who 

smoked during pregn sucy than for nonsmokers. But for both 

groups, as weight gain increases (up to 26–35 pounds), the risk 

declines (table Q). The fetal death ratio for nonsmokers was 

three times as high when weight gain was less than 16 pounds 

(10.8) as when weight gain was 26-35 pounds (3.4). For 

women who smoked during pregnancy, the fetal death ratio 

was 2% times as hQh for gains of less than 16 pounds (10.0) as 

for gains of 26-35 pounds (4.1). 

Because women who smoke are more likely than nonsmokers to deliver prematurely (before 37 weeks of gestation), 

fetal death ratios according to smoking habit and weight gain 

are shown by gestational period (less than 37 weeks, 37–39 

weeks, and 40 weeks or longer). For all gestational periods, 

there is a general pattern of lowered risk of fetal death for both 

smokers and nonsmokers as weight gain increases to 26–35 

pounds. For women who smoked delivering prematurely, the 

risk was reduced by 62 percent for weight gains of 26–35 

pounds compared with weight gains of less than 16 pounds 

(14.3 compared with 37.3); for gestational periods of 37-39 

weeks, the reduction in fetal death risk for a comparable increase in weight gain was 25 percen~ and for gestational periods 

of 40 weeks or longer, the reduction was 43 percent. 

As noted earlier, maternal size is strongly related to weight 

gain. Women in the sample who smoked during pregnancy were 

more likely to have a low weight-for-height index than nonsmoking mothers. Therefore, fetal death ratios are also shown 

for mothers who have a low, average, or high prepregnancy 

weight for their height (table R). For all three groups, there is a 

generrd pattern of higher risk of a fetal death outcome for 

smokers than for nonsmokers, and a substantial reduction in 

this risk as weight gain increases, up to 26–35 pounds. Among 

smokers, the sharpest decline in risk with added weight gain 

was found for women who had a low weight for their height. 

For these women, the fetal death ratio was 3?4 times as high for 

gains of less than 16 pounds (9.8) than for gains of 26–35 

pounds (2.8). 

A previous study of white mothers in the NFMS and 

NNS17 found that after controlling for differences in the mother’s 

prepregnancy weight and age, in the trimester prenatal care 

begrm, in the period of gestation, and in total-birth order, white 

women who gained less than 21 pounds were 1?4times as likely 

to have a fetal death outcome as white women who gained 

more. When the analysis was limited to white married women, 

this 50-percent higher risk did not change when differences in 

smoking habit were also taken into account. 

16 
--

--

------

Under 32 weeks 

.-. 32-35 weeks 

— 36 weeks 

60 

50 

40 

I 

30 

t20 

3 

1~


. . . . . . All gestational periods 

-m 37-39 weeks 

40 weeks and over 

--w 

/% ‘- %4H \ 

\ 

\ 

-\ 

�\e 

Less 16-20 21-25 26-35 36 

than pounds pounds pounds pounds 

16 or 

pounda more 

Figure 5. Fetel death ratios by weight gain during pregnanoy and 

period of gestation United States, 1980 National Natality and 

Fetal Mortality Surveys 

17 
Table N, Fetal death ratios by weight gain during pregnancy, prepregnancy weight, and race of mother: United States, 1980 National Natality 

and Fetal Mortality Surveys 

[Ratios are late fetal deaths per 1,000 live births] 

Weight gain during pregnancy 

Less 

than 16 16-20 27-25 26-35 36 pounds 

Race and prepregnancy weight of mother Total pounds pounds pounds pounds or more 

Allracesl .,,..............,.. . . . . . . . . . . . . . . . . . . . 5.2 0,5 6.7 4.8 3.8 4.1 

Less than l 10 pounds...,..,.. 4.3 1.6 6.5 3.8 2.8 3.6 

110-129 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 1.2 6.4 4.6 3.3 3.4 

130–149 pounds,..,..:...:.. . . . . . . . . . . . . . . . . . . . 5.1 0.2 7.2 5.2 3.9 4.1 

150–169 pounds, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 7.1 6.0 5.2 5.6 4.2 

170pounds or more ., ..,..,... . . . . . . . . . . . 8.2 2.2 7.2 6.0 6.1 7.0 

White ..,....,,.,,,,,.,,,,.,,. . . . . . . . . . . . . . 4.8 0.1 6.4 4.5 3.6 3.8 

Less than l 10 pounds ..,.,,.,, . . . . . . . . . . 4.2 9.6 6.3 3.6 3.2 3.4 

110–129 pounds,..,..,,.,,,, . . . . . . . . . . . . . . . 4.3 1.0 6.4 4.4 3.3 3.3 

130–149 pounds.........,,,, ., .,, ,,, ,, ...,...,. 4.9 1,4 7.3 4.7 3.7 3.8 

150–16900un do...,...,.,,, 4.8 6.4 5.7 4.3 4.6 3.9 

170p0unds OrmOre . . . . . . . . . . . 7.4 11.3 5.5 6.4 5.2 6.6 

Black ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 11.8 8.3 6.8 4.9 5.8 

Less than l 10 pounds . .,.,,..,. . . . . . . . . . . . . . . . . . 5.5 *24.8 *8.4 *4.4 “1.7 *4.4 

110–129 pounds, , .,, .,..,.., . . . . . . . . . . . . . . . . 5.9 10.9 7.3 6.7 3.3 5.1 

130-149 pounds,...,,,,,,,,, . . . . . . . . . . . . . . . . . . . . . . . 6.6 8.3 *6.9 8.9 4.8 6.1 

150–169 pounds, , ., ..,,.,.,, . . . . . . . . . . . . . . . . 9.5 10.2 *7.8 “11.4 ‘14.9 5.7 

170pounds or more. , . .,.,,..,, . . . . . . . . . . . . . . . . . . 10.7 15.0 *1 4.7 *4.8 *9.5 8.1 

Ilncludes races other than white and black 

Table O. Fetal death ratios bywaight gain during pregnancy andagaofmothec Unitad States, 1980 National Natality and Fetal 

Mortality Surveys 

[Ratios are late fetal deaths per 1,000 live births] 

Weight gain during pregnancy 

Less 

than 16 76-20 21-25 26-35 36 pounds 

Age of mother Total pounds pounds pounds pounds or more 

Alleges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 10.5 6.7 4.8 3.8 4.1 

Under 20 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 8.1 7.4 4.0 3.9 4.7 

20-24 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4,6 10.4 5.7 4.8 3.5 3.7 

25-29 years .,, .,, .,, ,, .,,..., 4,6 9.4 6.1 4.7 3.4 3.7 

30 years and over . . . . . . . . . . . . . . 6,8 13.8 8.2 5.9 5.0 5.1 

18 
Table P. Fetal death ratios by weight gain during pregnancy, period of gestation, and educational attainment of mothe~ Unitad States, 1980 

National Natality and Fetal MortaIity Surveys 

[Ratios are late fetal deaths per 1,000 live births] 

Weight gain during pregnancy 

Less 

than 76 16-20 2 7–25 26-35 36 pounds 

Period of gestation and years of school completed by mother Total 

Allgestational periods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 

O-n years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 

12 yeara . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 

13 years and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 

Under 37 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.3 

O-n years, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.5 

12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.9 

13 years and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.5 

37weeks andovar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 

O-n years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 

12yaars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 

13 years and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 

pounds pounds pounds pounds or more 

10.5 6.7 4.8 3.8 4.1 

9.6 7.0 5.7 4.5 5.1 

10.9 6.9 5.3 4.0 4.0 

10.9 6.1 3.8 3.2 3.5 

34.0 27.2 22.0 16.5 17.7 

26.3 28.9 18.0 15.7 20.0 

36.0 26.7 25.1 16.9 16.6 

46.4 26.5 22.1 16.8 17.6 

5.0 3.4 2.9 2.6 3.2 

5.0 3.8 3.7 3.0 4.0 

5.2 3.4 3.2 2.8 3.2 

4.6 3.2 2.2 2.3 2.8 

Table Q Fetal death ratios by weight gain during pregnancy, period of gestation, and smoking habit of married mothers: United States, 1980 

National Natality and Fetal Mortality Surveys 

[Ratios are late fetal deaths per 1,000 live birrha] 

Period of gestation and smoking habit of mothar 

Allgestational periods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Under 37 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smokar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

40 weeks And over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Weight gain during pregnancy 

Less 

than 76 16-20 21–25 26-35 36 pounds 

Total pounds pounds pounds pounds or more 

4.9 10.5 6.7 4.7 3.6 3.9 

5.6 10.0 7.2 5.2 4.1 4.7 

4.7 10.8 6.4 4.5 3.4 3.6 

24.7 38.3 31.6 24.2 16.0 18.5 

24.8 37.3 33.0 26.9 14.3 21.4 

24.6 38.9 31.0 23.3 16.8 17.0 

3.2 5.4 3.5 3.4 2.7 2.7 

3.3 4.4 3.3 3.1 3.3 2.7 

3.2 5.9 3.5 3.5 2.6 2.7 

3.0 4.8 3.5 2.5 2.5 3.2 

3.5 4.7 4.3 3.0 2.7 3.8 

2.9 4.9 3.2 2.3 2.4 3.0 

Table R. Fetal death ratios by weight gain during pregnancy, weight-for-height index, and smoking habit of married mothers: United Statea, 

1980 National Natality and Fetal Mortality Surveys 

[Ratios are late fetal deaths per 1,000 live births] 

Waight gain during pregnancy 

Less 

than 16 16-20 2 1–25 26-35 36 pounds 

Weight-for-height indexl and smoking habit Total pounds pounds pounds pounds or more 

All births . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9 10.5 6.7 4.7 3.6 3.9 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 10.0 7.2 5.2 4.1 4.7 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 10.8 6.4 4.5 3.4 3.6 

Lowwaight for height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 11.3 6.8 3.8 2.8 3.5 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 9.8 9.8 4.2 2.8 *4.4 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.9 12.0 5.9 3.6 2.8 3.2 

Average weight for height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 9.6 6.8 4.8 3.5 3.5 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 9.2 6.9 6.0 4.5 4.4 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 9.8 6.8 4.5 3.2 3.2 

High weight for height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6 11.0 6.3 5.5 5.1 5.2 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.0 10.6 6.1 5.2 5.5 5.9 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 11.1 6.4 5.6 4.9 5.0 

1Low is less than 25th percentile in study group, average is 25th-74th percentile, and high is 75th percentile or higher. 

19 
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IqpoPulation Information Program, Johns Hopkins University. Tcbacco-Hazards to health and human reproduction. Population Reports. Series L (1). Baltimore, Md. Mar. 1979. 

1‘lNational Center for Health Statistics: Unpublished tabulations. 

15National Center for Health Statistic~ Vital Wzdstics of the fJnited 

States, 1980, Vol. II, Mortality. Part A. DHHS Pub, No. (PHS) 85-

1101. Public Health Service. Hyattsville, Md. 1985. 

lbInstitute of Medicine; National Academy of Sciences Preventing 

Low Birthweight. Washington. National Academy Press, 1985. 

17S. M. TatTel and K. G. Keppek Implications of Mother’s Weight 

Gain on the Outcome of Pregnancy. Paper presented at the Annual 

Meeting of the American Statistical Association. Philadelphia. Aug. 

13-16, 1984. 

18Nationa[ Center for Health Statistics, K. G. Keppel, R. L. Heuser, 

P. J. Placek, et al.: Methods and response characteristic 1980 National Natality and Fetal Mortality Surveys. Vital and Health Statistics. Series 2, No. 100. DHHS Pub. No. (PHS) 86–1 374. Public 

Health Service, DHHS, Hyattsville, Md. In preparation. 

19M. H. Hansen, W. N. Hurwitz, and W. G. Madow: sample SurveY 

Methods and Theory, Vol. 1. New York. John Wiley and Sons, 1953. 

Zow. G. Cockan: Sampling Techniques. New York. John WileY and 

Sons, 1953. 

20 
Appendix 

Technical notes 

Sources of data 

The data presented in this report are based on the 1980 

National Natality Survey (NNS) and the 1980 National Fetal 

Mortality Survey (NFMS) conducted by the National Center 

for Health Statistics. A detailed description of the methods and 

procedures employed in these surveys can be found in “Methods 

and response characteristics: 1980 National Natality and Fetal 

Mortality 1g These notes briefly describe SurveY Pro- Surveys. Y?

cedures relevant to this report. 

The NNS is based on a probability sample of registered 

live births in the United States for the year 1980. .Approximately 1 in 95 infants weighing less than 2,500 grams and 1 in 

400 infants of higher birth weights were selected for the sample. 

The oversampling of low-birth-weight infants was to aid in the 

analysis of this high-risk group. Overall, the NNS sample consists of 9,941 live births, or approximately 1 in every 363 live 

births. The NFMS is based on a probability sample of registered 

fetal deaths occurring in 1980 with a physician’s estimate of 

gestation of 28 weeks or more or, when this information on 

gestation was lacking, with delivery weight of 1,000 grams or 

more. The sample consists of 6,386 fetal deaths, representing 

approximately 1 in 3 late fetal deaths in 1980. 

Information beyond that available from the certificates of 

live birth and reports of fetal death was sought from sources 

named on these vital records. Questionnaires were mailed to 

married mothers requesting information on their prenatal health 

practices, prenatal care, previous pregnancies, and on social 

and demographic characteristics. To ensure their privacy, 

mothers who were not married were not contacted. 

Regardless of the mother’s marital status, questionnaires 

were mailed to the hospital and to the attendant at delivery 

named on the vital record. A questiomaire was sent to the 

hospital for all deliveries that occurred in a hospital or en route 

to a hospital. A questionnaire was also mailed to the attendant 

at delivery (physician, nurse-midwife, etc.) for those deliveries 

where the attendant’s address was not the same as the address 

of the hospital. If the hospital or the attendant had little or no 

information concerning prenatal care, the name and address of 

another facility or individual that could provide this information 

were requested and questionnaires were sent accordingly. 

Because the provider of prenatal care is considered the 

most reliable source of information on weight gain during pregnancy, this report is based only on mothers for whom informatNOTE A list of references follows the text. 

ion on prenatal care was available (9,811 for the NNS sample 

and 6,150 for the NFMS sample). Information on the mother’s 

smoking habit, income, and height is available only from the 

mother’s questionnaire, so some of the analyses are limited to 

married mothers who received prenatal care (7,774 for the 

NNS and 4,699 for the NFMS). Hospitals and/or attendants 

at delivery supplied information on the mother’s prepregnancy 

weight and her weight at delive~, which were used to derive 

the weight gain during pregnancy. Married women were also 

asked to provide their weight before pregnancy and before delivery. If the medical sources failed to provide the mothefs 

weights, values were derived from the mother’s data, when 

available. Otherwise, the data were imputed on the basis of the 

mother’s age and race and the period of gestation. 

The NNS and NFMS data have been weighted to provide 

estimates for the appropriate populations of live births and fetal 

deaths in the United States in 1980. The estimates in this report 

represent all mothers for whom prenatal care information 

was available (3,580,596 for the NNS and 18,508 for the 

NFMS) or married mothers for whom information was available (2,929,71 3 for the NNS and 14,439 for the NFMS). 

About 1 percent of the live births and 4 percent of the late fetal 

deaths were excluded from this study because information on 

prenatal care was lacking. 

Definition of terms 

Low birth weight—Low birth weight is defined as less 

than 2,500 grams or 5 pounds 8 ounces. 

Fetal death ratio—The fetal death ratio is defined as the 

number of fetal deaths with a physician’s estimate of gestation 

of 28 weeks or more or delivery weight of 1,000 grams or more 

when physician’s estimate is not reported (late fetal deaths) per 

1,000 live births. These ratios differ from those published annually in Vital Statistics of the United States, Volume II, 

Mortality, which are fetal deaths of 20 weeks or more gestation 

per 1,000 live births. 

Weight-for-height index—This is a measure of maternal 

size computed from the formula 

where	 W= mother’s prepregnant weight in pounds 

H= mother’s height in inches 

21 
Low represents the first quartile of the study population; average, the second and thkd quartileq and h& the fourth quartile. 

Race—In all tables, race refers to the race of the mother. 

The category “white” comprises mothers whose race was reported as white, Mexican, Puerto Rican, Cuban, or other 

Hispanic origin. 

Sampling error 

Because NNS and NFMS estimates are based on a sample, 

they may differ from the figures that would have been obtained 

had all live births and fetal deaths been surveyed. The use of 

probability sampling techniques makes it possible to approximate sampling errors for these estimates. 

The standard error is a measure of the variability that occurs 

by chance because a sample rather than the entire population is 

surveyed. While the standard errors calculated for this report 

reflect some of the random variation inherent in the measurement process, they do not measure any systematic error, or 

bias, that may be present in the data. 

The chances are about 68 out of 100 that an estimate from 

the sample differs by less than one standard error from the 

figure that would be obtained from a complete census of all 

births or fetal deaths; the chances are about 95 out of 100 that 

the estimate differs by less than two standard errors. The relative. 

standard error of an estimate is obtained by dividing the standard error of an estimate by the estimate itself, and can be expressed as a percent. In this report an estimate is considered 

unreliable if it is based on less than 30 sample cases, or if its 

relative standard error is 25 percent or greater. For purposes of 

this report, standard errors were estimated using a balanced 

repeated replication technique. This technique produces highly 

reliable, unbiased estimates of sampling emors. Its application 

to the NNS and NFMS is described elsewhere. 18 

Standard errors for estimated mean weight gains and mean 

birth weights are included in tables A-E. The standard errors 

NOTE: A list of references follows the text. 

for mean birth weights in table F are shown in table I, and for 

mean birth weights in tables K and L, in table II. Sampling 

errors for other aggregates, percents, and fetal death ratios in 

this report can be calculated according to the procedures described in the sections that follow. Weighted numbers of women 

needed to compute standard errors for the percent low birth 

weight in tables G-J and for the fetal death ratios in tables M-P 

are shown in table III, and for fetal death.ratios in tables Q and 

~ in table IV. 

Aggregates 

Tc) approximate the relative standard error (RSEX) and the 

standard error (SEX) of an estimated number of live births or 

fetal deaths, the appropriate values of A and B from table V are 

to be used in the following equations 

and 

SEX= X < RSEX 

where x = the estimated number of live births or fetal deaths. 

This formula should not be used to compute sampling errors for 

estimates of less than 10,890 live births or ’90 fetal deaths, ap 

proximately 30 sample cases. 

Percents 

To approximate the relative standard error (RSEP) and the 

standard error ( SEP) of a percentp, the appropriate values of B 

from table V are to be used in the following equations 

B 100–p RSEP . d. — 

PY 

SEP = P “RSEP 

Table 1. Standard errors for estimated mean birth weight of live births by weight gain during pregnancy, period of gestation, and race of 

mothec United States, 1980 National Natality Survey 

Weight gain during pregnancy 

Less than 16-20 21-25 26-35 36 pounds 

Race of mother and period of gestation Total 16 pounds pounds pounds pounds or more 

Grams 

Allracesl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 20 19 13 10 12 

Llnder37 weeks.............,.. . . . . . . . . . . . . . . . . . . 24 63 56 24 40 82 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 26 24 23 16 23 

40 weeks and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 17 21 19 18 13 

White . . . . . . . . . . . . . . . . . . . . . . . . . . 8 25 22 15 11 13 

Under 37 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 69 79 45 44 81 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 41 31 26 16 26 

40waeks And over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 21 23 ‘ 22 20 15 

Black . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 28 36 36 25 31 

Under 37 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 119 100 62 79 158 

37-39 weaks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 49 94 47 46 39 

40weeka and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 37 58 77 47 56 

1Includes races other than white and black. 

22 
-wherep = 1()()x/y= the estimated percent. The approximation 

of the relative standard error or the standard error of a percent 

is valid only when one of the following conditions is satisfied 

(a) the relative standard error of the denominator is 5 percent 

or less,lg or (b) the relative standard errors of the numerator 

and the denominator are both 10 percent or less.zo 

Fetal death ratios 

The relative standard errors of the numerator (N) and the 

denominator (D) of the fetal death ratio are calculated as pre 

viously described for aggregate estimates. The relative standard 

error (RSE,) and the standard error (SE,) of the fetal death 

ratio r can then be approximated using the following equations: 

RSE, = /( RSE~)2 + (RSED)2 

and 

SE, = r .RSE, 

fetal deaths 

‘here r = live births .1,000 

RSE~ = RSE of numerator (fetal deaths) 

RSED = RSE of denominator (live births) 

The approximation of the absolute or relative standard error of 

a ratio estimate is valid only when either of the two conditions 

noted for percent estimates is satisfied. 

NOTE A list of references follows the text. 

Testing differences 

In this report, a difference between two statistics is considered statistically significant if it could occur by chance no 

more than 5 percent of the time. The determination of statistical 

significance is based on a two-tailed t-test with 20 degrees of 

freedom. At the 0.05 (5-percent) level, the critical value for the 

t-test is 2.09. Terms relating to differences such as “higher,” or 

“less,” indicate that the differences are statistically significant. 

Terms such as “similar” or “no difference” mean that no statistically significant difference exists between the estimates being 

compared. No inference about statistical significance should 

be made about any differences not discussed in the tex~ they 

may or may not be significant. 

The standard error of a difference between two statistics is 

approximately the square root of the sum of the squares of the 

standard errors of the two statistics being compared. This formulation quite accurately approximates the standard error for 

the difference between uncorrelated statistics, although it only 

roughly approximates the standard error in most other cases. 

The number of replicates used in the balanced repeated replication technique (20) can be used to approximate the number of 

degrees of freedom when testing hypotheses about differences 

between estimated statistics. A tw~tailed test with 20 degrees 

of freedom is used throughout this report. 

Example—In 1980, an estimated 10.5 percent of the 

2,917,000 white mothers giving birth gained less than 16 pounds 

during their pregnancy compared with 20.0 percent of the 

554,000 black mothers gaining this amount. The standard 

errors for the two estimates of percents are 0.38 and 1.34, respectively. To determine whether there is a statistically signjfiTable Ii. Standard errors for estimated mean birth weight of live births to married mothers by weight gain during pregnancy, period of gestation, 

weight-for-height index, and smoking habit United States, 1980 National Natality Survey 

Period of gestation,


weight- for-height index, 1 and smoking habit


All mothers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker ; . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Under 37 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

40 weeks and over. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Lowweight for height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Average weight for height . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

High weight for height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Smoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Nonsmoker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Weight gain during pregnancy 

Less than 16-20 2 1–25 26-35 36 pounds 

Total 16 pounds pounds pounds pounds or more 

Grams 

9 23 19 15 12 15 

10 38 41 24 20 25 

10 36 21 17 13 14 

27 78 82 43 46 92 

73 128 194 120 82 139 

37 110 87 45 53 109 

11 31 26 26 17 27 

18 43 39 49 24 46 

14 48 37 32 20 32 

11 24 23 19 21 15 

20 52 65 29 26 34 

12 37 28 25 22 15 

11 59 40 34 22 24 

16 106 101 44 32 39 

14 68 39 39 24 28 

10 37 22 20 15 21 

18 50 53 38 31 39 

11 54 25 23 16 19 

17 33 49 36 35 25 

29 65 110 41 56 55 

22 44 44 48 43 28 

I Low is less than 25th percentile for study group, average is 25th-74th percentile, and high is 75th percentile or higher. 

23 
Table Ill. Number of live births by selected characteristics: Unitad States, 1980 National Natality Survey 

Weight gain during pregnancy 

Less than 16-20 21-25 26-35 36 pounds 

Selected characteristic Total 16 pounds pounds pounds pounds or more 

RACE Number in thousands 

All racesl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -. 3,581 428 408 613 1,242 889 

White . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,917 306 323 505 1,034 750 

black . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554 111 70 89 166 118 

PREPREGNANCY WEIGHT 

All racesl 

Less than 110 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478 38 56 96 185 103 

110-129 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,315 103 150 235 519 308 

130-149 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 968 97 103 155 332 281 

150-169 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441 81 50 67 120 122 

170pounds or more . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 109 50 60 86 75 

White 

Less than 110 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372 29 45 73 140 85 

110-129 pounds . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,094 71 119 197 439 267 

130-149 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 791 62 80 134 279 236 

150-169 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 63 40 58 108 102 

170pounds ormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 81 40 43 67 59 

Black 

Less than l 10 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 6 7 18 28 13 

110-129 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 29 25 27 64 33 

130-149 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 32 20 19 45 38 

150-169 pounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 16 9 9 12 19 

170 pounds or more . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..!. B5 27 9 16 18 15 

YEARS OF SCHOOLING OF MOTHER 

Under 37weeks of gestation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 81 55 61 104 53 

O-n years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 32 14 19 29 13 

12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 35 26 25 47 27 

13years ormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 14 16 17 28 13 

37weeks ofgestation And over.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,226 347 353 552 1,138 836 

O-n years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 770 114 94 115 219 167 

12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,421 151 148 240 486 395 

13years ormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,096 82 111 197 433 273 

PERlOO OF GESTATION 

Under 32 weeka . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 24 12 10 11 7 

32-35 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 36 25 26 53 24 

36weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 21 18 25 40 23 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,238 156 147 224 446 266 

40weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 869 82 92 149 323 223 

41 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528 45 55 97 181 151 

42 weeks and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 591 65 59 82 189 196 

AGE OF MOTHER 

Under 20years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55’3 79 65 99 173 136 

20-24 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,215 139 130 198 416 331 

25-29 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,101 114 122 192 407 266 

30years and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 712 96 91 125 245 155 

YEARS OF SCHOOLING OF MOTHER 

All ages 

Less than 12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 817 146 108 134 248 180 

12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.579 186 173 265 533 422 

13-15 yeara . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 676 63 77 123 244 168 

16years ormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 33 49 91 217 119 

Mothers 20years ofage and over. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,028 349 343 514 1,069 753 

Less than 12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480 92 68 76 143 102 

12 yeara . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,380 163 154 229 469 367 

13-15 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659 61 73 118 240 166 

16years or more . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 33 49 91 217 118 

Ilncludea racea other than white and black. 

24 
Average

Average

Table IV. Number of live births to married mothers by selected characteristics: United States, 1980 National Natality Survey 

Weight gain during pregnancy 

Less than 16–20 21-25 26-35 36 pounds 

Selected maternal characteristic Total 16 pounds Pounds Dounds Dounds or more 

SMOKING HABIT Number in thousands 

All births . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,930 311 326 501 1,048 744 

Smokers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767 104 91 121 254 198 

Nonsmokers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,162 207 235 380 794 546 

PERIOD OF GESTATION 

All births 

Under 37 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 51 37 43 78 41 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,023 111 119 182 383 228 

40 weeks and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,657 149 170 275 587 475 

Smoker 

Under 37 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 17 10 11 26 14 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 36 35 45 90 56 

40 weeks And over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426 51 45 64 138 128 

Nonsmoker 

Under 37 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 34 27 32 52 26 

37-39 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 760 74 83 137 293 173 

40 weeks and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,231 99 125 211 449 348 

WEIGHT-FOR-HEIGHT INOEX1 

All mothers 

Low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726 46 76 138 291 175 

High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,478 113 154 243 562 407 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726 153 96 119 195 162 

Smoker 

Low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 16 17 39 90 54 

Average High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 39 47 52 120 100 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 50 27 30 44 44 

Nonsmoker 

Low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 30 59 99 201 121 

High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,121 74 107 191 442 307 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532 103 70 89 151 119 

1Low is less than 25th percentile for study group, average is 25th-74th percentile, and high is 75th percentile or higher, 

cant difference in weight gain by race, compute 

20.0 – 10.5 

t= /(0.38)2+ (1.34)2= 6“82 

Because the two-tailed 0.05 critical value for a t-statistic with 

20 degrees of freedom is 2.09, the difference in weight gain by 

race is statistically significant at the 0.05 level. 

Nonsampling error 

Estimates based on the NNS and NFMS are also subject 

to nonsampling errors. The sources of nonsampling error include incomplete coveragq misinterpretation of questions; incomplete or inaccurate responseq and errors in coding, editing, 

Table V. Parameters used to compute relative standard errors for 

live births and fetal deaths by maternal characteristic 

Parameter 

Maternal characteristic A B 

Live births to unmarried mothers and 

to mothers of races other than 

white . . . . . . . . . . . . . . . . . . . . . . . . . . – 0.00054674 390.07705 

Live births to married mothers, to 

white mothers, and to all 

mothers . . . . . . . . . . . . . . . . . . . . . . . – 0.00010438 377.81921 

Fetal deaths . . . . . . . . . . . . . . . . . . . . . -0.00019317 3.71310 

keying and imputing for nonresponse. Although the extent of 

these nonsampling errors cannot be measured, the procedures 

employed in the INNS and NFMS were designed to minimize 

them. .. 

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Vital and Health Statistics 

series descriptions 

SERIES 1. 

SERIES 2. 

SERIES 3. 

SERIES 4. 

SERIES 5. 

SERIES 10. 

SERIES 11. 

SERIES 12. 

SERIES 13. 

Programs and Collection Procedures—Reports describing 

the general programs of the Natio~al Cen{er for Health 

Statistics and its offices and divisions and the data collection methods used. They also include definitions and 

other material necessary for understanding the data. 

Data Evaluation and Methods Research—Studies of new 

statistical methodology including experimental tests of 

new survey methods, studies of vital statistics collection 

methods, naw analytical techniques, objective evaluations 

of reliability of collected data, and contributions to 

statistical theory. Studies also include comparison of 

U.S. methodology with those of other countries. 

Analytical and Epide,miological Studies—Reports presenting analytical or interpretive studies based on vital 

and health statistics, carrying the analysis further than 

the expository types of reports in the other series. 

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 certificates. 

Comparative Internationai Vital and Health Statistics 

Repotis-Analytical and descriptive reports comparing 

U.S. vital and health statistics with those of other countries, 

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 intewiew sutvey. 

Data From the National Health Examination Survey and 

the National Health and Nutrition Examination Survey— 

Data from direct examinat~on, testing, and measurement 

of national samples of the civilian noninstitutional ized 

population provide” the basis for (1) estimates of the 

medically defined prevalence of specific diseases in the 

United States and the distributions of the population 

with respect to physical, physiological, and paychoIogical characteristics and (2) analysis of relationships 

among the various measurements without reference to 

an explicit finite universe of persons. 

Data From the Institutionalized Population Sumeys-Discontinued in 1975. Reports from these suweys are included in Series 13. 

Data on Health Resources Utilization—Statistics on the 

utilization of health manpower and facilities providing 

long-term care, ambulatory care, hospital care, and family 

planning sewices. 

SERIES 14. 

SERIES 15. 

SERIES 20. 

SERIES 21. 

SERIES 22. 

SERIES 23. 

For answers 

. 

Data on Health Resources: Manpower and FaciIities— 

Statistics on the numbers, geographic distribution, and 

characteristics of health resources including physicians, 

dentists, nurses, other health occupations, hospitals, 

nursing homes, and outpatient facilities. 

Data From Spatial Surveys-Stak.tics on health and 

health-related topics collected in special s~rveys that 

are not a part of the continuing data systems of the 

National Center for Health Statistics. 

Data on Mortality-Various statistics on mortality other 

than as included in regular annual or monthly reports. 

Special analyaes 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 suweys of those 

records. 

Data on Natality, Marriage, and Divorce—Various statistics on natality, marriage, and divorce other than as 

included in regular annual or monthly reports. Special 

analyses by demographic variables; geographic and time 

series analyses; studies of fertility; and statistics on 

characteristics of births not available from the vital 

records based on sample suweys of those records. 

Data From the National Mortality and Natality Survays— 

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 suwey of a nationwide 

probability sample of ever-married women 15–44 years 

of age. 

to questions about this report or for a list of titles of 

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National Center for Health Statistics


Public Health Service


Hyattsville, Md. 20782


301-436-8500


I