SERUM LEPTIN CONCENTRATIONS DURING PREGNANCY AND THEIR RELATIONSHIP TO FETAL GROWTH

Objective: To test the hypothesis that maternal and cord serum leptin concentrations correlate with birth weight of infants. Methods: Pregna nt women (n = 135) of low socioeconomic status who delivered full-term infants were selected from more than 1500 women who participated in a study to identify factors related to fetal growth restriction (FGR). They were divided into two groups based on their infants being classif ied as having FGR (n = 66) or not (n = 69), and each group was divided further into three subgroups based on prepregnancy body mass index (B MI): less than 19.8, 19.8-28.9, and 29 or more. Sample estimations ind icated that 20 subjects per subgroup would be adequate to detect 50% d ifference in leptin concentrations. Results: Mean maternal serum lepti n concentrations adjusted for BMI were highest at approximately 22-27 weeks' gestation (29.8 ng/mL) and declined thereafter until term (25.2 ng/mL). Leptin concentration and prepregnancy BMI correlated signific antly. We found neither significant difference in leptin concentration s between the subjects with and without FGR infants nor significant co rrelation between maternal leptin concentrations and birth weight of i nfants. Mean cord serum leptin concentration (10.8 ng/mL) was lower th an maternal concentrations and correlated significantly with birth wei ght (r = .61, P < .001). Conclusion: Our findings suggest that materna l leptin concentration during pregnancy is not an accurate indicator o f fetal growth. Cord serum leptin concentrations were lower than mater nal serum concentrations and correlated significantly with birth weigh t. (C) 1998 by The American College of Obstetricians and Gynecologists .