Maternal Serum Leptin During Pregnancy and Infant Birth Weight: the Influence of Maternal Overweight and Obesity

Few studies have examined whether the distinct metabolic patterns found in obese and non-obese pregnant women may have different effects on the growing fetus. Our objective was to estimate the influence of longitudinal variation in maternal serum leptin levels on variation in infant birth weight in overweight/obese versus normal weight women. In a prospective cohort of 286 gravidas, we measured maternal weight and serum leptin levels at 6–10,10–14,16–20, 22–26, and 32–36 weeks gestation. Effects of leptin levels on infant birth weight adjusted for gestational age at delivery (aBW) were analyzed using a linear regression model that accounted for the relationship of time-varying predictors to the log transformed leptin concentrations. Overweight/obese and normal weight gravidas exhibit different relationships of aBW to maternal serum leptin and its rate of change across pregnancy. For normal weight women, aBW is not associated with either the magnitude of the logarithm of the leptin concentration nor with its rate of change in either the first or second half of pregnancy. Conversely, for overweight/obese women, we find that an increase in the rate of change in maternal serum leptin in the second half of pregnancy is significantly associated with a decrease in aBW. We find that this effect is distinct from that of maternal weight. Differences in the effect of maternal serum leptin on fetal growth between overweight/obese and normal weight women suggest metabolic and physiologic heterogeneity between these groups. Such differences may be involved in the long-term physiologic effects of the obese intrauterine environment on the health of the offspring.