(Received November 10, 1969; revision accepted for publication January 26, 1970.)
Supported in part by Contract No. PHS4368-10 with the National Institutes of Health, Public Health
Service, and U.S. Public Health Service Grant HD 3957-01, Department of Health, Education and
Welfare.
ADDRESS FOR REPRINTS: (S.C.B.) Department of Pediatrics, University of Oregon Medical School, Portland, Oregon 97201.
PEDIATRICS, Vol. 45, No. 6, June 1970 937
FETAL
GROWTH
Liveborn
Birth
Weights
for
Gestational
Age
of
White
Middle
Class
Infants
S. Gorham Babson, M.D., Richard E. Behrman, M.D.,
and Richard Lessel, M.P.H.
Departments of Pediatrics and Public Health, University of Oregon Medical School, Portland, Oregon; and the Department of Pediatrics, University of Illinois College of Medicine, Chicago
ABSTRACT. Fetal growth in weight is presented on 40,000 single, newborn infants between 27 and 44 weeks’ gestational age. They were delivered of white mothers who lived near sea level and re-ceived obstetric care from private physicians. Their mean birth weights were greater at term and after
term than previously reported in the United States and were similar to those presented from the Scan-dinavian countries. Pediatrics, 45:937, 1970, NEW,
BORN INFANTS, BIRTH WEIGHT OF NEWBORN
IN-FANTS, FETAL GROWTH, GESTATIONAL AGE OF IN-FANTS.
C
LASSIFICATION of infants at birth byweight alone is not as satisfactory for predicting mortality risks as the use of both weight and gestational age.1’2 Variations in infant mortality rates3#{176} and in the fre-quency of various types of problems7 are
dependent in part upon an infants’ size for gestational age, physical maturity, and sex. There is considerable variation in published weight-gestational data and several points of disagreement among authors owing in large measure to differences in the
popula-tions studied and the methods of data
col-lection.6,8h1 In general, these reports are
based upon populations that include a sub-stantial proportion of women from lower socioeconomic backgrounds who
presum-ably have had minimal prenatal health care. This study provides a description of changing weights with gestational age dur-ing human pregnancy in a group of 40,000
white, single infants born to middle class
mothers in the United States who received prenatal care from physicians in private
practice.
SAMPLE AND METHODS
The sample used represents all deliveries
in two maternity hospitals#{176} in Portland,
Ore-gon, from 1959 through 1966, with the ex-ception of the year 1964 in which several months’ records were misplaced. The
moth-ers were primarily of Northern European
descent and received private prenatal care; and, more than 80% of them were deliv-ered by obstetricians. The other infants were delivered by general practitioners.
With few exceptions, the women lived near
sea level.
The gestational age to the nearest week was calculated from the first day of the last
menstrual period as stated in a history
ob-tained from the mother and recorded prior
to delivery. In about 60% the precise day of the beginning of the last menstrual was
known. In no more than 10% the histories
were ambiguous and the obstetricians, in
making estimates of the expected time of
I)aia Tot at
Population
Unrecorded
MuLtiple Gestation Non-white
Births Weight or <o Weeks EDC
Study
Sample
Males 22,061 1,058 387 12 2 20,602 328
Females 20,737 1,058 379 7 0 19,293 225
Total 42,798 9,116 766 19 2 39,895 553
Neonatal Deaths
2$ 30
-
32 34 36 3$ 40 WoOs of Gesfotioo42 44
TABLE I
TOTAL POPULATION OF LIVEBORN INFANTS FitoM WIlIeR STUDY SAMPLF WERE DRAWN
delivery, took into consideration such signs
as uterine size, initial observation of fetal
heart beat, and time of quickening. In the remaining mothers the menstrual period was identified within a few days of its ac-tual occurrence, i.e., first, middle, or last week of a specific month. Thus, the
fre-quency of unrecorded estimates of
gesta-tional age is low and indicates those women in whom neither clinical estimation of fetal age or calculations from menstrual informa-tion could he made with reasonable
accu-racy. We would have preferred to report
gestation in completed weeks as recom-mended by the World Health Organization; but, the gestational ages of the hospital
FIG. 1. Distribution curve of single, white new-born infants for each week of gestational age as
calculated to the nearest week.
data were reported to the nearest week, as were most of the studies used for compari-sons.
Unclothed infants were weighed in pounds and ounces on admission to the
nurs-eries. Birth information was placed on the
standard birth certificate forms, which in turn were coded by the Vital Statistic See-tion of the Oregon State Board of Health. The applicable data from these cards were placed on magnetic tapes at the Oregon Re-gional Primate Center. A computer
pro-gram was used to convert weights to the
metric system and to calculate means and
standard deviations as well as percentiles for first born and subsequently born infants of both sexes at the two hospitals. Since there were no appreciable differences in
overall mean weights of the infants in the two hospitals, the data from them were combined for analysis. Fetal deaths, multi-ple births, and infants of other than white mothers were excluded from the statistical analysis. Table I lists general data of the population of liveborn infants from which the study samples were derived.
RESULTS
Table II presents the mean and standard
deviation and percentiles of the birth weights calculated for all infants from 27 through 44 weeks of gestation. The number of liveborn infants whose gestational ages were from 20 to 26 weeks (125) and over 44 weeks (29) was considered insufficient
Fig-q3V5.
400C -y -
-
,,-350C
300C
-
--
-(____
I
z
///
95
90
75
50
25
-. /0 5
‘1
-
I5OC- Iooc
-,/
a
.._L__
/7
CVV_7/7
-_I__
p.-...L....
26 28 30 32 34 36 38
Weeks of Gestation
40 42 44
weeks 28-29 30-3/ 32-33 34-35 36-37 38-39 40-4/
0 2.0 2.5
.25 .75 1.25 1.75 2.25 2.75 3.25 3.75 4.25 4.75
Birthweight in kg
3.0 3.5 4.0 4.5
5
#{188}
. ‘5
#{188}
PERCENTIL ES
‘5..
‘5 1.
#{188}
‘5
Fic. 2. Percentile curves of fetal growth in weight in relation to the
gesta-tional age (which is calculated to the nearest week) for a white, middle
class population.
5.0
Gesta-tional
.lge
(uk)
Number
of
P(IIiCflts
Stan-Mean dard
(gin)
Devia-lion 5th
Percentiles
10th 25th 50th 75th 90th 95th
27 3() 1,034 217 593 687 837 1,022 1,193 1,375 1,468
28 47 1,172 344 597 695 929 1,118 1,302 1,691 1,887
29 39 1,322 339 871 993 1,102 1,275 1,450 1,893 ‘2,012
30 78 1,521) 474 824 1,034 1,255 1,458 1,742 2,024 2,381
31 69 1,757 495 1,076 1,184 1,408 1,648 1,968 2,443 2,818
32 105 1,881 437 1,269 1,351 1,578 1,861 2,134 2,453 ‘2,734
33 127 2,158 511 1,504 1,588 1,812 2,095 ‘2,407 2,893 3,145
34 228 2,34() 552 1,542 1,746 1,986 2,298 ‘2,683 3,104 3,424
35 317 2,518 468 1,S(ht 1,943 ‘2,245 ‘2,489 2,8()6 3,137 3,329
31; 841 2,749 490 ‘2,033 2,173 ‘2,4()6 ‘2,697 3,044 3,414 3,661
37 1,499 ‘2,989 466 2,258 2,392 ‘2,657 ‘2,960 3,286 3,620 3,793
38 3,761 3,185 450 ‘2,468 9,6()2 2,875 3,171 3,466 3,745 3,958
39 6,609 3,333 444 ‘2,582 2,763 3,044 3,325 3,623 3,902 4,090
40 15,691 3,462 456 ‘2,720 2,880 3,150 3,448 3,745 4,045 4,246
41 6,047 3,569 468 2,813 3,003 3,254 3,547 3,870 4,186 4,392
42 3,144 ‘3,637 482 ‘2,851 3,039 3,306 3,618 3,934 4,288 4,478
43 881 3,660 502 2,817 3,014 3,309 3,652 3,966 4,330 4,499
44 ‘229 3,619 515 ‘2,758 2,962 3,278 3,589 3,966 4,252 4,517
TABLE II
ACTUAL WEIGhT VALUES FOR 40,000 SINGLE, WhITE, MIDDLE (‘IAss INFANTS
(GESTATIONAL AGE WAS CALCULATED TO TILE NEsltFsT WEEK)
ure 1 presents the percentage distribution of all births for each week of gestation.
Fig-ure 2 shows the weights at birth graphed as percentiles for each gestational age.
Figure 3 presents a distribution curve of birth weights by 250 gm groups for
concur-rent two-week combination of gestational
age. There is a steeper, narrower curve as
gestation is shortened.
Figure 4 presents the percentile curves of fetal growth by sex. From 37 weeks on the separation in weight becomes more marked and by 40 weeks of gestation the average discrepancy in weight is about 150 gm.
DISCUSSION
The errors inherent in the determination of fetal growth rate are well known, even
when the menstrual history is accurate. Among them are a variation in length of
menstrual cycle, time of ovulation and
con-ception, and the mistakes in calculation or recording. Interpretation of vaginal bleed-ing during early pregnancy as a menstrual
period is a frequent source of error. The
care paid to the determination of the EDC
and the capabilities of women to recall menstrual information are factors deter-mining the precision of fetal growth data. Even then, measurement data are based on
those infants who are born at a particular
time which may not be representative of the fetal population still remaining in utero.
Figure 5 shows a comparison of the
me-dian percentile weight curves for Portland babies with those of Denver8 and Baltimore
(Sinai Hospital).#{176} After 37 weeks Portland babies are heavier than the other infants
re-ported from the United States, and after 40
weeks they are larger than British
in-fants.bo,hl In Figure 5 the 10th percentile curves of different populations in the United
90
50
4500
4000
3500
3000
2500
2000
1500
1000
-/0
_..#._ ...
/0,50,90 TN PERCENTILES
0-0 Males #{149}--. Females
FIG. 4. Percentile curves of fetal growth for boys and girls.
Our study has focused on a different and
more homogenous population than
pre-sented in previous reports. The data in the
reports from Newcastle,’1 New York State,4 and Baltimore (all city ) show an upward displacement in the 50th and 90th percentile
curves for infants delivered before term. This is not apparent in our data. Some pre-sumably premature infants, large for their gestational age, were omitted from the Denver data,8 and a correction factor was used in the Baltimore group9 to adjust for
this possible error.
Neliganhl and Gruenwald have
com-mented on the bimodal character of the
dis-tribution curves of weights for infants with shorter than usual gestational periods. They
attribute this bimodal distribution to in-stances of vaginal bleeding, which may
simulate a menstrual period, following an
established pregnancy. The distribution of
weight groups in the Portland data (Fig. 3)
shows a minor degree of this effect for
in-fants with the shorter gestational periods.
Careful history taking may eliminate some
discrepancies of this nature.
The curves of weight distribution become narrower as immaturity increases. When we superimpose comparable Portland data on
the distribution curves of Gruenwald and
Neligan11 (Fig. 6) for infants of the same gestational age, the peaks of the Portland curves coincide with the first rise of the other two curves. This feature lends
sup-‘5
#{188}
. .‘3’
‘3
#{188}
I I I I I I I I I J_
34 36 38 40 42 44
/0
‘-5
Portland
Bolt im ore Denver
38 40 42 44
GESTATIONAL AGE 32±l.5wk
30
5,.. ‘5
20
I..)
#{188}
‘5
Q 0
Por//ond
GESTATIONAL AGE 30±O.5wk
wold Ne//gon
2.0 3.0 4.0 5.0 1.0 2.0 3.0 4.0 5.0
Fic. 6. Comparison of birth weight distribution curves for populations with the same gestational age.
4500-4000
3500
5#
C #{188} ‘55
2500
‘55
‘5
#{188} 3000
2000
500
1000
PERCENTIL ES
I I I I I I I I I 11111
28 30 32 34 36
Weeks of Gestation
FIG. .5. Comparisons of fetal weight curves for different population in the United States.
port to their inference that many larger and more mature infants have been erroneously included in their premature groups and may partially explain the high mean birth
weight of premature infants in less selected populations.6’1’
Kloosterman’2 has presented data which suggest that fetuses of Dutch women have
‘5 ‘5
an optimal intra-uterine environment in that they continue to grow, although at a lesser rate, through the post-term period. Fetal growth in Swedish13’” and Finnish15 reports increases through the period of time
similar to that seen in the Portland data,
but none of their curves of growth reach
the level found in Dutch fetuses after term has been passed.
Gruenwald and co-workers’6 have predi-cated that the normal fetal growth curve during the third trimester would be linear until term is reached if the supply of
nu-trients to the fetus were adequate. In this
sequential study on Japanese babies, the
improvement in maternal health may have increased the weight of infants at term.
Linear growth for the fetus during World
War II continued only until 35 to 36
weeks of gestation, whereas by 1963 to 1964
fetal growth continued unchecked to 38 weeks. The mean growth in Portland babies
appears to continue unabated to at least 38
weeks of fetal age.
SUMMARY
Weight-gestation data are presented for
nearly 40,000 single, white live births.
These infants, born at sea level, were deliv-ered in two private hospitals. In our opin-ion, the standards of obstetric practice in
these hospitals was good. The socioeco-nomic status of these families was at least middle class.
Means, standard deviations, and
percen-tile curves are presented for infants from 27 through 44 weeks of gestation. Comparisons are also made with reported data from other population groupings within the United States and abroad.
These birth weight data, when inter-preted as a measure of fetal growth for this population, appear to indicate that: (1) the newborn infants reported in this study are heavier at maturity than those previously reported from the United States; (2) boys weighed more than girls after 37 weeks of gestation. At 40 weeks of gestation the
mean weight of male infants is 3,534 gm
and is approximately 150 gm more than
that of girls (3,389 gm ); (3 ) curves of weight distribution for the gestational ages
studied were relatively smooth and bell-shaped, and the curves became narrower
and steeper as weeks of gestation were
shorter.
REFERENCES
1. Battaglia, F. C., and Lubchenco, L. 0. : A practical classification of infants by weight and gestational age. J. Pediat., 71 : 159, 1967. 2. Yerushalmy, J., Van den Berg, B. J., Erhardt,
C. L., and Jacobziner, H. : Birth weight and gestation as mrlices of “immaturity.” Amer.
1. Dis. Child., 43:109, 1965.
3. Van den Berg, B. J., and Yerushalmv, J.:The relationship of the rate of intrauterine growth of infants of low birth weight to mortality, morbidity, and congenital anoma-lies. J. Pediat., 69:531, 1966.
4. Ehrhardt, C. L., Joshi, C. B., Nelson, F. C., Kroll, B. I-I., and Weiner, L. : Influence of weight and gestation on perinatal and
neo-natal mortality by ethnic group. Amer. J.
Public Health, 54: 1841, 1964.
5. Behrman, R. E., Babson, S. G., and Lessel, R.: Perinatal death in a middle class, white pop-ulation. Unpublished manuscript.
6. Battaglia, F. C., Frazier, T. M., and Hellegers, A. E. : Birth weight, gestational age, and pregnancy outcome, with special reference
to high-birth-weight-low-gestational-age
in-fants. PEDIATIucs, 3:717, 1966.
7. Lubchenco, L. 0., llansman, C., and
Bach-strom, L. : Factors influencing fetal growth.
In Jonxis, J. H. P., Visser, H K. A., and Troelstra, J. A., ed. : Aspects of Prematurity and Dysmaturity ( Nutricia Symposium). Springfield, Illinois: Charles C Thomas, pp.
263-280, 1968.
8. Lubchenco, L. 0., llansman, C., Dressier, \I., and Boyd, E.: Intrauterine growth as esti-mated from liveborn birth-weight (lata at 24 to 42 weeks of gestation. PEDIATRICs, 82:
793, 1963.
9. Gruenwald, P.: Growth of the human fetus. I. Normal growth and its variation. Amer. J. Obstet. Gynec., 94:1112, 1966.
10. Butler, N.: Perinatal death. Clin. Devel. Med., 19:74, 1965.
11. Neligan, G.: A community study of the rela-tionship between birth and weight and gesta-tional age. Clin. Devel. Med., 19:28, 1965. 12. Kloosterman, G. J.: The obstetrician and
944
13. Lindell, A.: Prolonged pregnancy. Acta Obstet. Gynec. Scand., 35:136, 1956.
14. Engstr#{246}m, L., and Sterky, C.: Standard kurvor
for vikt och langd hos nyfodda barn, Sar-treck ur Lak, 63:4922, 1966.
15. Rantakallio, P.: Groups at risk in low birth
weight infants and perinatal mortality. Acta Pediat. Scand. (Suppl. 193), 58, 1969.
16. Gruenwald, P., Funakawa, H., Mitani, S.,
Nishimura, T., and Takeuchi, S.: Influence
of environmental factors on foetal growth in man. Lancet, 1:1026, 1967.
Acknowledgment
Miss Marion M. Martin, M.P.H., Director of Vi-tal Statistics, State of Oregon, gave valuable aid.
WHAT AILED SAM STONE’S INFANT SON?
No physician of eminence came to this
coun-try during the seventeenth century. Medicine
was practiced either l)y clergymen, or the
Cob-nial Governors; both, at best, were only partly
trained as physicians.1
The pathetic letter below, exactly as written
by the child’s father, was sent to John
Win-throp, the Younger ( 1606-1676) . This letter
is typical of those Winthrop often received
from desperate parents who had no other
source of medical advice for their children. Worthie Sir
I am bold to write a few lines about our child.
he is 23 weeks old, hath been somewhat ill 3 or 4 weeks, unquiet, his eyes looking yellow, having a cough, especially when he takes his vistuals. wee thought he might have been breeding teeth: but about a week past we peceived yt. [that] he had the yellow Jaundise. By Mrs. Hooker her advice we gave him Barbaric barke boyled in beer, wth saf-fron, twice a day, for two dayes together. & one time saffron alone. Also lice 2 or 3 times [once thought
to be of therapeutic value in jaundice] & Tumerick twice. we hoped yt. the Jaundise had been cured: because he was sometimes more cheareful &had a better appetite, but the last Saterdaie at night he was very unquiet heavie & could not sleep & upon
the Sabbath seemed to looke somewhat swart
[flushed] in the face. In the afternoone we gave
him about 3 quarters of a grain of your purging powder, which we had of Mrs. haynes which caused him to vomit twice or thrice, & to purge downwards thrice. he slept well the night after & in the morning was somewhat unquiet again as before, wringing & winding back. his cough seems to increase, as if he had much fleagme. he seems to be sick at times but without any conulsion [sic] or starting fits. when he began to be ill, he was costive in his bodie, but now is in good temper. he doth bume often but a little sometimes.
I pray Sir send me word whether he may not
take some more of that pouder & what quantity. If
you thinke it conveient to prescribe anything I
pray speake to Mr. Blinman I know he will peure some Indian to bring your note & I will please him for his journey. I am much indebted to you for your kind entertainment of me when I was wth you: we remember our service to yourselfe & Mrs. winthrop, & our respect to Mr. Lake wth our love to Mr. Blinman & hoping yt we shall see you in our pts shortly I rest.
Your servant in Christ SAM: STONE Hartford ffebr. 28, 1652.
Nrn’ED BY T. E. C., Ja., M.D.
REFERENCE
1. Viets, II. R.: A Brief History of Medicine in
Massachusetts. Boston: Houghton Muffin
