Fetal growth retardation in relation to maternal smoking and weight gain in pregnancy.

Two types of fetal growth retardation were recognized in term infants. One type was characterized by an abnormally low ponderal index (defined as birth weight in grams X 100 divided by crown-heel length in cubic centimeters.) The other type of growth-retarded infants had abnormally short crown-heel lengths for fetal age. Both types were observed under all conditions studied. However, mothers who smoked cigarettes during pregnancy were more likely to have infants with short body lengths for dates, whereas mothers who had low weight gain in pregnancy were more likely to have infants with low ponderal indices. Social group, prepregnancy weight, parity, marital status, and fetal sex were found to be less determinant of fetal growth than were maternal weight gain and smoking habits.