Fetal growth retardation was diagnosed in 137 (7.8 percent) of 1,757 white full-term infants who had crown-heel lengths below the fifth percentiles for their gestational ages. The incidence of short infants was 121 (11.1 percent) among 1,093 mothers with high-risk pregnancies compared to 16 (2.4 percent) in 664 low-risk mothers (p less than 0.0001). There were four high-risk categories: spontaneous premature rupture of membranes (PROM), fetal conditions, complications of pregnancy, and adverse maternal practices. The incidence of short infants was significantly higher in each of the four high-risk categories than in the low-risk group. There were three other conditions that were present in all pregnancies that were associated with the frequency of short infants: maternal height, socioeconomic status of head of household, and sex of infant. A short maternal height (under 157.7 cm = 62 inches) was significantly associated with an increase in short infants among mothers who smoked cigarettes at any level during pregnancy and among mothers with PROM in combination with other risks, but not in the group of 664 low-risk mothers. Significantly more short girls than short boys were born to mothers who smoked ten or more cigarettes a day throughout pregnancy or who had multiple adverse maternal practices, but no statistically significant differences were noted among mothers who smoked fewer than ten cigarettes per day, among those with PROM as the only risk factor, or among those with medical or obstetrical complications. Moreover, those mothers who were in socioeconomic groups III and IV and had other risk factors had a significantly higher incidence of short infants than did similar mothers in socioeconomic groups I and II.
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