A positive umbilical venous-arterial difference of leptin level and its rapid decline after birth

OBJECTIVE: We investigated the site of leptin production in the fetoplacental circulation. STUDY DESIGN: We simultaneously determined plasma leptin levels in cord vessels and maternal peripheral veins of 38 healthy pregnant women. We also compared plasma leptin levels in 20 neonates at birth and on the fifth day after birth. RESULTS: Leptin levels in cord vessels were significantly (p < 0.001) lower than those in maternal veins (mean 29.5 ng/ml). Leptin levels in umbilical arteries (mean 9.8 ng/ml) were significantly (p < 0.01) lower than those in umbilical veins (mean 12.9 ng/ml). Leptin levels in neonatal veins on the fifth day (mean 3.0 ng/ml) were markedly (p < 0.001) lower than those in umbilical arteries of the same neonates (mean 10.9 ng/ml). CONCLUSION: The higher leptin levels in umbilical veins than in umbilical arteries and the marked decrease during the neonatal period suggest that the placenta is one of the major sources of leptin in the fetal circulation.