Sex related effects of nutritional supplementation during pregnancy on fetal growth

Nutritional supplementation of low income women during pregnancy increased birth weight significantly only in the male offspring. No differences by sex were apparent in the amount of supplementation, length of gestation or maternal characteristics known to be associated with birth weight. Regression analysis revealed a significant supplementation by sex interaction. The fetal growth curve of the supplemented males was higher and roughly parallel to the curve of females, and showed an effect of supplementation prior to 35 weeks of gestation. These findings and those of other authors support the hypothesis that fetal growth of males towards the end of pregnancy is more rapid and hence more susceptible to adverse environmental influences than that of females. This is reflected in a reduction of the difference in birth weight in favor of males observed in well-nourished populations. It is postulated that male subjects therefore exhibit sensitivity to nutritional supplementation of their mothers during pregnancy.