Umbilical Venous Leptin Concentration and Gender in Newborns

Objective: To investigate the relationship between umbilical venous leptin concentration and gender in 20 pairs of newborns matched 1:1 for birth weight and gestational age at sampling. Materials: Blood samples were obtained from 40 women at delivery, identified as having an uncomplicated pregnancy. Umbilical venous blood samples were obtained from their newborns (20 females and 20females) at birth. Specimens were analyzed using a human leptin 125-I radioimmunoassay. Results: Fetal leptin correlated positively with birth weight (r_s= 0.541; P < .001). Umbilical venous leptin concentrations in female newborns (median: 10.7 ng/mL, range: 3.5-34.4 ng/mL) were significantly higher (P= .028) than in male newborns (median: 7.7 ng/mL, range: 2.0-19.3 ng/mL). There was no significant correlation between maternal and fetal leptin concentrations. Multiple logistic regression analysis revealed birth weight and gender to be independent factors influencing fetal cord leptin. Conclusion: Our results suggest that in the fetus, as in children and adults, gender and weight are the major determinants of circulating leptin levels.