Fetal plasma leptin concentrations: Relationship with different intrauterine growth patterns from 19 weeks to term

The relationship between in utero fetal growth and fetal leptin concentrati ons was investigated between 19 and 41 wk in 40 normal (appropriate for ges tational age, AGA) fetuses, in 25 intrauterine growth-restricted (IUGR) fet uses, and in 18 fetuses from gestational diabetic mothers (GDM), representi ng different intrauterine growth patterns. Umbilical venous plasma leptin c oncentrations were determined at the time of either in utero fetal blood sa mpling or delivery. Plasma leptin was measurable as early as 19 wk of gesta tion. A significant difference was observed between umbilical venous and ar terial plasma leptin concentrations (0.6 +/- 0.6 ng/mL; p < 0.01). In AGA a nd in IUGR fetuses, significant positive relationships were found between f etal leptin concentrations and both gestational age (p < 0.001) and fetal w eight (p < 0.001). Leptin concentrations were significantly higher in AGA t han IUGR only after 34 wk (p < 0.05), but leptin per kilogram fetal weight (leptin/kg) was not significantly different. In IUGR with abnormal umbilica l arterial Doppler velocimetry and fetal heart rate, leptin/kg significantl y higher than in IUGR with normal biophysical and biochemical parameters wa s found (p < 0.05). Both circulating plasma leptin and leptin/kg were signi ficantly higher in GDM than in normal fetuses (p < 0.001) and correlated wi th abdominal fat mass measured by ultrasound. No gender differences were ob served in any group of fetuses. These findings indicate a clear relationshi p between fetal leptin concentrations and fetal fat mass. Data in severe IU GR suggest the presence of increased leptin concentrations associated with in utero signs of fetal distress.