Objective:To study the relationship between leptin concentration and fetal growth.Methods:Levels of leptin in maternal serum,amniotic fluid,arterial and venouscord blood of 65 normal parturients (gestational age 37-42weeks) were measured by ra-dioimmunoassay (RIA) method.At the same time,maternal blood lipids were detected.Neonates were divided into three groups:small for gestational age (SGA) group (n=10),appropriate for gestational age (AGA) group (n=45),large for gestational age(LGA) group (n=10).Statistical analysis was performed by t test,variance analysisand correlation analysis.Results:(1) There was no obvious correlation between leptin concentrations in ma-ternal serum and arterial/ venous cord blood,amniotic fluid,and also no correlationwith birth weight and placental weight (P>0.05).Maternal body mass index signifi-cantly correlated with birth weight and neonatal length and leptin levels in arterial andvenous cord blood (P<0.01).Leptin levels in arterial and venous cord blood positivelycorrelated significantly with placental and neonatal weight and body length (P<0.01)and negatively correlated with high density lipoprotein (P<0.01).There was no obvi-ous correlation between fetal gender and leptin concentrations in maternal serum,arteri-al and venous cord blood and amniotic fluid;(2) Leptin levels in arterial and venouscord blood,placental weight in LGA group were significantly higher than those in SGAand AGA group (P<0.05).Among three groups,leptin concentrations in maternalblood were significantly higher than those in arterial and venous cord blood (P<0.05).Conclusions:(1)Fetal leptin is synthesized in uterus,born of itself and placenta.Leptin levels in arterial and venous cord blood are related to the intrauterine growthpattern.It might positively regulate birth weight and body fat content.(2)Either mater-nal or fetal leptin was not correlated with fetal gender.There is no gender difference infetal leptin concentrations.