Objective: The purpose of this study was to determine the relationship of neonatal sex and gestational diabetes mellitus on cord leptin concentration and to determine whether cord leptin has a stronger correlation with fat mass compared with birth weight or lean body mass. We hypothesized that there are no significant differences in fetal leptin concentration between male and female or between neonates of mothers with gestational diabetes mellitus and control neonates, when adjusted for body composition.
Study design: Cord blood leptin concentrations were measured in newborn infants of 78 women (44 control neonates and 34 gestational diabetes mellitus). Of the 78 neonates, 32 babies were female, and 46 babies were male. Birth weights were measured with a calibrated scale, and body compositions were measured by total body electrical conductivity.
Results: Estimated mean gestational age at delivery was 39.1 +/- 1.1 weeks for control neonates versus 38.6 +/- 1.3 weeks for neonates of mothers with gestational diabetes mellitus (P =.01). The fat mass for the control neonates and neonates of mothers with gestational diabetes mellitus was 0.36 +/- 0.15 kg versus 0.48 +/- 0.21 kg (P =.01); the percent body fat for the control neonates and neonates of mothers with gestational diabetes mellitus was 10.5% +/- 3.8% versus 13.2% +/- 4.3% (P =.006), respectively. There was no significant difference in cord leptin concentration between male and female neonates (16.0 +/- 13.8 ng/dL vs 12.7 +/- 12.8 ng/dL, P =.24). Cord leptin concentrations (18.1 +/- 16.2 ng/dL vs 10.9 +/- 9.5 ng/dL, P =.02) were significantly greater in neonates of mothers with gestational diabetes mellitus than in control neonates. In all subjects, cord leptin was significantly correlated with percent body fat (r = 0.51, P <.0001), fat mass (r = 0.49,P <.0001), and birth weight (r = 0.25, P =.03). After the adjustment for fat mass, there was no significant difference in cord leptin concentration between control neonates and neonates of mothers with gestational diabetes mellitus (P =.20), but there was a significant difference between male and female neonates (P =.04). However, when an adjustment was made for both fat mass and lean body mass, there was no longer a significant difference between male and female neonates (P =.12)
Conclusion: The differences in cord leptin concentration between male and female neonates and between infants of women with gestational diabetes mellitus and control neonates are related to differences in body composition.