Physical
Maturity
and Outcome
of Pregnancy
in
Primiparas
Younger
Than
16 Years
of Age
Aurapin C. Sukanich, MD, Kenneth D. Rogers, MD, and
Hugh M. McDonald, MD
From the Departments of Community Medicine and Pediatrics, University of Pittsburgh,
Pittsburgh
ABSTRACT. The association of complications and
ad-verse outcomes of early teenage pregnancy with physical growth maturation of mothers was studied in subjects identified from review of medical records in a Pittsburgh obstetrical hospital from 1970 through 1977. Five groups were used to categorize the subjects: (1) 449 primiparas younger than 16 years of age, (2) 347 primiparas 20 to 24 years of age, pair-matched with subjects in group 1 by
race, hospital service status, sex of infant, trimester of
first prenatal visit, and year of delivery within 5 years,
(3) 139 group 1 mothers at the time of their second delivery, (4) 104 group 1 primiparas whose postmenar-cheal age was 2.6 years at delivery, and (5) 108 group 1 primiparas whose postmenarcheal age was 4.1 years at delivery. Subjects in groups 1 and 2, first ind second pregnancies of subjects in group 3, and subjects in groups
4 and 5 were compared for prepregnancy weight and height, weight gain during pregnancy, complications of pregnancy, birth weight and gestational age of infant,
and perinatal morbidity and mortality. Although
primi-paras younger than 16 years of age had not achieved mature height and weight, no relationship between moth-er’s physical growth maturation and adverse pregnancy course or outcome was demonstrated. Pediatrics
1986;78:31-36; early adolescent pregnancy, physical ma-turity, pregnancy outcome.
Pregnancy in young adolescents occurs fre-quently in the United States. In 1981, there were
9,632 live births to mothers younger than 15 years of age and 187,397 live births to mothers 15 to 17
years of age.1 Although adverse medical outcomes such as pregnancy-induced hypertension and low
birth weight infants have been reported for early
teenage pregnancy,24 it is not clear whether these
Received for publication March 25, 1985; accepted Aug 26, 1985. Presented at the Annual Meeting of the Ambulatory Pediatric Association Washington, DC, May 13, 1982.
Reprint requests to (A.C.S.) Department of Community
Medi-cine M-200 Scaife Hall, Pittsburgh, PA 15213.
PEDIATRICS (ISSN 0031 4005). Copyright © 1986 by the American Academy of Pediatrics.
associations are due to biologic immaturity and inadequacy or to confounding factors such as low socioeconomic status, poor nutrition, and made-quate prenatal care.
Mice,5 rats,6 pigs,7 cattle,8 horses,9 and rhesus
monkeys’#{176} can conceive at their first ovulation and before they have achieved mature size. Nutrition prior to conception and during pregnancy is an important determinant of pregnancy outcome in
these animals. Those with good nutrition carry pregnancy to term and have normal pregnancy
outcome in spite of their young age.7’8
The questions investigated in this study were whether young teenage primiparas had achieved full
body growth and, if not, whether less than mature body sizes was associated with complications and adverse pregnancy outcomes. Three sets of
compar-isons were used to contrast less mature with more mature women with respect to body size, pregnancy
experience, and pregnancy outcome: (1) primiparas
younger than 16 years of age at delivery (teenage primiparas) were compared with primiparas 20 to
24 years of age, (2) teenaged primiparas were
com-pared with themselves at the time of their second
pregnancy, and (3) teenage primiparas with
men-arche 2.6 years or less prior to delivery were
com-pared with teenage primiparas of the same chron-ologic age whose menarche had been 4.1 years or
more before delivery.
METHODS
Source of Data
Since 1970, the Department of Pediatrics at
Ma-gee Women’s Hospital, Pittsburgh, routinely ab-stracted maternal demographic, obstetrical, and newborn infant data from records of all deliveries
of infants weighing more than 500 g. For deliveries
without maternal or infant complications, records
Mother Mother
<16 yr of age 20-24 yr of age
(n = 509) (n = 7067)
I
1
I
‘1
Excluded Study Study Not Studied
(n = 60) (n = 449) (n= 347) (n = 6720)
Group 1 n = 449 Description
Group 2 n = 347 Matched
comparison Group 3 n = 139 Second pregnancy
Group 4 n = 104 Postmenarcheal age 2.6 yr Group 5 n = 108 Postmenarcheal age 4.1 yr
Figure. Study population. Primiparous pregnancies, 1970 to 1977. Infants’ birth weights >500 g.
using standard definitions and criteria developed
by staff neonatologists. In complicated cases,
phy-sicians reviewed the records and coded the
infor-mation using the same coding criteria. All coded
information was transferred to a computer data file.
Study Population
Records were identified, from the computer data,
of all primiparas who, between 1970 and 1977, delivered infants weighing more than 500 g. Women with abortion prior to their first delivery, twin
pregnancies, and medical problems prior to
preg-nancy (eg, diabetes mellitus, seizure disorder on medication, systemic lupus erythematosus,
hyper-thyroidism, hypertension) were excluded from the
study population. Data collection was begun in October 1979.
Each primipara younger than 16 years of age at delivery was matched, in order of sequence of her hospital unit number, to a primipara 20 to 24 years of age who had the same race, hospital service status, sex of infant, trimester of first prenatal visit, and year of delivery within 5 years. If more than
one 20- to 24-year-old woman matched the teenage
subject, selection of the matching subject was made
using random numbers.
All second pregnancies of primiparas younger than 16 years that occurred during the study period
were identified for comparison with first pregnan-cies. The age at menarche, when noted in the med-ical record, was used to calculate a postmenarcheal
age by subtracting menarcheal age from age at delivery.
The composition of the study population is
rep-resented in the Figure.
Data Quality and Completeness
The validity of the computerized data relative to that in the original clinical record was assessed by having a pediatrician (A.C.S.) independently
ab-stract and code 51 randomly selected records using the original coding criteria. Only items that showed at least 90% agreement and were available for 80% to 100% of all patients were used in this study. Data from the computerized file included: Mother’s
data-race, hospital service status (private, nonpri-vate service), marital status; numbers of previous pregnancies and abortions, onset of labor, cesarean
section, placenta previa, abruptio placentae,
ante-partum hemorrhage, ruptured uterus, hypotension, pregnancy induced hypertension, maternal death,
and puerperal infection. Infants data-sex, Apgar score at five minutes, birth weight, placental ab-normality, fetal distress, stillbirth, neonatal death,
fetal malnutrition, asphyxia, respiratory distress syndrome, hyperbibirubinemia, anemia, hypogbuco-semia, hypocalcemia, and major congenital anom-alies.
Additional data needed for the study were
di-rectly abstracted from clinical charts, using a
pre-coded form, and then entered in the data file.
Ad-ditional data directly abstracted from clinical charts included mother’s birth date and delivery date, age
at menarche, dates of last menstrual period, first
prenatal visit, last prenatal visit, prepregnant
weight (by history at time of first prenatal visit),
height (without shoes, by measurement at time of
first prenatal visit); weight at last prenatal visit
within 4 weeks of delivery; infant gestational age
by pediatric examination (Dubowitz method). Two abstractors achieved at least 90% agreement on all
items coded independently from 50 randomly
se-lected charts. Because most of the primiparas
younger than 16 years old did not commence
pre-natal care until after the first trimester of
preg-nancy, prepregnant weight was defined as that
re-ported by the patient at the time of first visit. The validity of these estimates was investigated by
com-paring the prenatal weight stated by history and
the weight at time of first visit in all (N = 21)
com-menced care in the first trimester. The same obser-vations were made for the 21 primiparas 20 to 24
years of age with whom the younger primiparas
were matched. There were no statistically signifi-cant differences (P = 0.8 and 0.9, paired t test)
between prepregnant weight reported historically and weight at time of first trimester visit in women in either group.
Analysis
Student’s t test was used to test statistical
signif-icance for continuous variables such as birth weight and length of gestation, and the
x2
test was used todetermine statistical significance for nominal
van-abbes such as presence or absence of cesarean
sec-tion and respiratory distress syndrome.
RESULTS
Study Population
Teenage Primiparas. There were 296 primiparas
15 years of age and 153 14 years and younger. Of
these mothers, 317 (71%) were black and 132 (29%)
were white. Eighty-one percent were of low socio-economic status (nonpnivate service) and 91% were
unmarried. Six percent of these young teenage
pni-miparas made no prenatal visits, and 6%, 57%, and 31 % started their prenatal visits in the first, second, and third trimester, respectively. Young teenage pnimiparas bore almost equal numbers of male and female infants.
Older Primiparas. A total of 347 primiparas
younger than 16 years old were pair-matched with
the same number of mothers 20 to 24 years of age at first delivery. There were no differences in ma-ternal age, hospital service status, or sex of infants between the 102 teenage primiparas who could not be matched and the 347 who were matched. There were, however, more black mothers (82% v 67%)
and more mothers who either had no prenatal visits or started their prenatal care in the third trimester oftheir pregnancies (42% v 28%) in the unmatched
group
(x2
1 df, P < .01). The average age atmen-arche was 1 1.8 years in young teenage pnimiparas and 12.8 years in 20- to 24-year-old pnimiparas (t test, P < .001).
Second Pregnancies. One hundred thirty-nine
young teenage primiparas had records of a second
delivery 1 to 7 years after the first (mean: 3 years).
The mean maternal ages at first and second delivery
were 15.2 and 18.3 years, respectively. Mothers in
their first and second pregnancies had similar so-cioeconomic status and trimester of first prenatal
visit. More mothers were married at the time of
their second pregnancy than their first one.
Menarcheal Age. Age at menarche was recorded
for 421 of the total 449 teenage primiparas (94.1%)
and ranged from 8 to 15 years (average 11.8 years). The mean postmenarcheal age (age at delivery
mi-nus age at menarche) was 3.5 years, (range 0.8 to
7.1 years) and the 25th, 50th, and 75th percentile in postmenarcheal ages were 2.6, 3.4, and 4.1 years,
respectively. There were 104 mothers with
post-menarcheab age 2.6 years (low postmenarcheal age group) and 108 with postmenarcheal age 4.1 years (high postmenarcheal age group). Average
chron-obogic age at delivery was 15.0 years in the low postmenarcheal age group and 15.4 years in the
high postmenarcheab age group (t test, P < .01).
More mothers in the bow postmenarcheal age group
were of bow economic status (97% v 85%) compared
with mothers in the high postmenarcheal age group
(x2 1 df, P < .005). Slightly more black mothers
were in the low postmenarcheal age group (76% v
68%), but the difference was not significant. Trimester of first prenatal visit and marital status
were similar in the two groups.
Maternal Height, Prepregnant Weight, and
Weight Gain During Pregnancy
Young teenage primiparas were shorter and weighed less at the time of their first pregnancy
when compared with themselves at the time of their
second pregnancy and with older primiparas. The
heights and weights of young teenage primiparas in the lowest quartile of postmenarcheal age did not differ significantly from those in the highest
quar-tile of postmenarcheal age (Table 1).
Weight gain during pregnancy was defined as the difference between prepregnant weight and weight
measured at last prenatal visit, within 4 weeks of delivery. The average gains in weight during
preg-nancy were not statistically different between the three comparison groups.
Maternal Complications
There were no statistically significant differences
in maternal complications of pregnancy among the
three compared groups except for greater incidence of pregnancy-induced hypertension in first preg-nancies of young teenagers compared with second
pregnancies (Table 2).
Pregnancy Outcome
The average birth weights of infants (Table 3) were not different statistically between the three
compared groups. The incidence of low birth weight
TABLE 1. Prepregnancy Weight, Height, and Weight Gain During Pregnancy
n
Primipara
<16 yr old 20-24 yr old n
Pregnancy
First Second n
Postmenarc 2.6 yr
heal Age n a4.1 yr
304 54.0 ± 7.4 59.6 ± 12.6 115 54.8 ± 8.7 57.0 ± 9.6 99 53.2 ± 7.5 99 54.6 ± 8.2
Prepregnant wt (kg,
mean ± SD)
Height (cm, mean ± 291 161.0 ± 7.0 163.6 ± 7.0 110 161.0 ± 7.6 162.0 ± 6.7 95 161.1 ± 8.2 94 159.5 ± 6.3 SD)
Wt gaint (kg, mean 302 13.0 ± 5.4 13.4 ± 6.2 115 12.1 ± 5.2 11.5 ± 6.5 99 12.7 ± 5.5 99 12.7 ± 4.8
± SD)
t Difference between prepregnant weight and weight measured at last prenatal visit, within 4 weeks of delivery.
* Age at delivery minus age at menarche. :1:Paired ttest, P < .001.
§Paired t test, P < .05.
TABLE 2. Maternal Complications*
Complication Primipara Pregnancy Postmena rcheal Age
<16 yr old
[n = 347]
20-24 yr old [n = 347]
First En= 139]
Second [n = 139]
2.6 yr En= 104J
4.1 yr
[n = 108]
Cesarean section
Abruptio placentae
Pregnancy-induced hypertension Endometritis
Temperature >38.3#{176}C[101#{176}F]
postpartum 25 (7.2) 4 (1.1) 14 (4.0) 2 (0.6) 4 (1.1) 27 (7.9) 3 (0.9) 17 (4.9) 5 (1.4) 4 (1.1) 8 (5.7) 1 (0.7) 9 (6.5) 1 (0.7) 1 (0.7) 12 (8.6) 2 (1.4) 2t (1.4) 6 (4.3) 1 (0.7) 12 (11.5) 4 (3.8) 4 (3.8) 1 (1.0) 2 (1.9) 4 (3.7) 0 (0.0) 5 (4.6) 0 (0.0) 1 (0.9)
* Results are numbers (percentage) of mothers. t McNemar’s x2 P < .025.
significantly different statistically (Tables 4 and 5).
Teenage primiparas had an average of 6.2 days shorter length of gestation (by dates) (P < .01) and 3.5 days shorter by pediatric examination (P < .05)
than older mothers. There were no differences in gestational ages of infants of teenage mothers in their first and second pregnancies, both by dates and by pediatric examination. Infants of mothers with bow postmenarcheab age had less gestational age by dates than those of mothers with high post-menarcheal age (P < .05). However, the difference
was not confirmed when gestationab age was deter-mined by pediatric examination (Table 3).
Incidence of neonatal complications and
perina-tab mortality were not significantly different statis-ticably between the three compared groups (Table 4).
DISCUSSION
The difference of 1.0 cm in height between first and second pregnancies (average growth rate of 0.37
cm/yr) and differences in height and weight of
teenage and older primiparas appear to support the
hypothesis that primiparas who were younger than
16 years of age had not achieved full body growth and, in this respect and to the degree shown, could
be considered not fully mature biologically. This
finding of incomplete growth is compatible with the observation of Bender,” in which gain in height after an early teenage pregnancy was reported.
It is also in agreement with the analysis of data from the National Collaborative Perinatab Project
(NCPP) of the National Institute of Neurological and Communicative Disorders and Stroke by Garn
et al.’2”3 The study, based on 11,464 teenage partic-ipants (13 to 19 years of age) and 28,477 older
participants (20 to 29 years of age), showed that teenage mothers were shorter and weighed less than older mothers.’2 When 1,601 teenage girls, 169 of whom were younger than 15 years, were followed longitudinally through two or three pregnancies, they found that changes in height and weight were
small but consistent with growth of girls after
men-arche.’3
Based on the assumption that weight gain during pregnancy reflected maternal nutritional status during pregnancy and that, in turn, nutritional status influenced fetal growth,’4 the observation
that young primiparas in this study had weight gain during their first pregnancy and infant birth weight comparable to those in their second pregnancy and to those of older primiparas suggests that these young primiparas, although not fully mature phys-icalby, were able to nourish both themselves and their fetuses adequately. These observations are in
agreement with studies in horses, cows, pigs, rats
and mice in which satisfactory pregnancies were achieved in animals with good nutrition who were bred before mature physical growth was attained.9
poor pregnancy outcomes in teenagers, often
preg-a,. nancy-induced hypertension and bow birth weight
c O#{149} infants,24 there were no major differences in this
,‘ +1 study in reproductive complications and outcomes
;
between younger and older mothers. Although the- Co CO length of gestation was shorter in younger than in
g older mothers, the average length of gestation in
:
, young mothers still was more than 37 weeks, that. a
2
is, full-term and not premature. Complicationscommon to premature infants such as respiratory
5 distress syndrome and asphyxia also were not more
‘ prevalent in young mothers compared with older
q +1 +1 +1 mothers. There may be several explanations as to
,1
why increased incidence of pregnancycomplica-tions in young primiparas were not observed in the present study when such had been reported in other
a studies. First, the present study compared groups
matched for a number of variables affecting
out-Cl’ come and may have matched out factors, such as
0 #{149} race, socioeconomic status, and amount of prenatal
i
;i
care, possibly associated with maternal age. Second,c .. C3 the young teenage primiparas in this study appar-Cfl , ently had sufficient food to permit both mother and
fetus to be nourished adequately and
noncompeti-‘ tively. Third, the young teenage primiparas in this
a c, study averaged about 3.5 years of postmenarche
4.’ td ‘ and perhaps were too mature to test the effects of
. +1 +1 +1 biologic immaturity.
c’i ‘-4
Young teenage primiparas in this study had their menarche at an earlier age than older women (11.8 years v 12.8 years, respectively). This confirms
pre-a vious findings that young pregnant teenagers are
‘-4 ‘-4 early-maturing girls, as reported by Hassan and
a’ Falls,’5 Duenhoeler et al,3 and Garn and Petzold.’2
-: There have been a few studies’6”7 that suggested
0L0 C’ ci . . . . .
+1 +1 +1 that high incidence of low birth weight infants was
Lq al. c1 associated with young postmenarcheab age at
con-ception and delivery. Contrary to these findings, in
co_ the present study, the incidence of low birth weight
:
I’
infants was not significantly different between the- low and high postmenarcheal age groups. In
addi-.o c’ tion, the postmenarcheal age groups had
compara-- ‘
;
ble prepregnant weight, height, and weight gain, during pregnancy, maternal complications, and
in-, fant outcomes. As previously noted, the young
pri-c mipara in this study may have been too mature to
a test hypotheses concerning biologic immaturity.
;, ,- u SUMMARY
.
_1
.‘a -‘ V V The present study showed that, although young
. - - -- - N C/) Ld primiparas had not achieved mature height and
+
i
c weight, they did not have outcomes of pregnancycw , 4’ 4” different from older primiparas. It appeared that
i
. +1 +1 fi , girls who were physiologically mature enough toci c. conceive did not have adverse pregnancy risks
TABLE 4. Infant Complications*
Complication Primipara Pregnancy Postmena rcheal Age
<16 yr old 20-24 yr old First Second 2.6 yr 4.1 yr [n = 347] [n = 347] En= 139] En= 139] En= 104] En = 108]
-
---Stillbirth 4 (1.1) 5 (1.4) 4 (2.9) 1 (0.7) 3 (2.9) 1 (0.9)
Neonatal death 5 (1.4) 4 (1.1) 4 (2.9) 6 (4.3) 3 (2.9) 1 (0.9)
Fetal distress 94 (27.1) 93 (26.8) 30 (21.6) 31 (22.3) 31 (29.8) 31 (28.7)
Apgar score <7 12 (3.5) 12 (3.5) 5 (3.6) 2 (1.4) 8 (7.7) 3 (2.8)
Respiratory distress 18 (5.2) 13 (3.7) 8 (5.7) 11 (7.9) 6 (5.8) 4 (3.7)
Asphyxia 12 (3.5) 15 (4.3) 5 (3.6) 3 (2.2) 6 (5.8) 4 (3.7)
Fetal malnutrition 11 (3.2) 16 (4.6) 6 (4.3) 6 (4.3) 3 (2.9) 4 (3.7)
Anemia 11 (3.2) 8 (2.3) 5 (3.6) 3 (2.2) 3 (2.9) 5 (4.6)
Hypoglucosemia 3 (0.9) 4 (1.1) 1 (0.7) 1 (0.7) 1 (1.0) 0 (0.0)
Hypocalcemia 7 (2.0) 4 (1.1) 2 (1.4) 3 (2.2) 3 (2.9) 4 (3.7)
Major congenital anomalies 7 (2.0) 8 (2.3) 2 (1.4) 5 (3.6) 0 (0.0) 1 (0.9)
Birth wt 2,50O g 44 (12.7) 41 (11.8) 27 (19.4) 27 (19.4) 19 (18.3) 12 (11.1)
* Results are numbers (percentage) of infants.
TABLE 5. Infants With Gestational Age 37 Weeks by Pediatric Examination*
Primipara Pregnancy Postmena rcheal Age
<16 yr old 20-24 yr old First Second 2.6 yr 4.1 yr (n = 124) (n= 124) (n= 120) (n = 120) (n = 93) (n = 88)
Gestational age 35 (28.2) 22 (17.7) 23 (19.2) 22 (18.3) 16 (17.2) 13 (14.8) :37 wk
* Results are numbers (percentage) of infants.
ability to conceive and carry a conceptus beyond
500 g seemed to indicate reproductive maturity, regardless of chronologic age or time interval
be-tween menarche and delivery. A relationship be-tween biologic immaturity and adverse pregnancy
experience and outcome was not demonstrated.
ACKNOWLEDGMENTS
We thank Margaret Gloninger, MS, Allan Drash, MD,
Julie Hotchkiss, PhD, Carol Redmond, ScD, Douglass
Thompson, MD, and Paul M. Taylor, MD, for their
advice: Paninee Terana, Shirley Ali, Rebecca Shapiro,
Robert Schwarzbach for data collection and processing; Floyd H. Taylor, ScD, for statistical advice; and Joanna Bresz for secretarial assistance.
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