Objective: To explore the relationship between leptin levels and fat mass at the time of birth to test the hypothesis that the level of leptin in the fetal circulation is primarily an index of fetal fat mass.
Methods: Leptin concentration was measured in cord blood obtained from the offspring of 42 women. Trimmed, drained placental weight and neonatal morphometrics were obtained after delivery.
Results: The ranges in maternal weight (46.7-93.2 kg), weight gain (3.2-22.6 kg), percent body fat (10-34%), placental weight (290-688 g), birth weight (2.63-4.32 kg), neonatal fat mass (179-782 g), and cord blood leptin (1.7-26.7 ng/mL) were wide. The only morphometric variable that explained a significant portion of the variation in cord blood leptin levels was neonatal fat mass (r2 = 0.41), and this relationship was not significantly improved by best subset regression of additional fetal and placental morphometric variables (r2 = 0.46).
Conclusion: These data support the hypothesis and suggest that in the fetus, as in the child and the adult, fat mass is the major determinant of circulating leptin levels.