Abstract： Objective　To study the role of placental leptin in intrauterine cord leptin production and its relationship with neonatal anthropometry. Methods　Forty women and their babies (40) were enrolled in this study. Placental tissues were assayed for leptin mRNA by reverse transcription/polymerase chain reaction (RT/PCR), and assayed for the obese gene protein leptin by Western-blot and immunohistochemistry. Blood was taken from the umbilical cord of the babies at delivery. Serum leptin was measured by radio-immunoassay. Neonatal anthropometric measurements were recorded within 48 hours after delivery. Linear regression analysis was used to explore the relationship between placental leptin, cord leptin and neonatal anthropometric measures. Results　The obese gene was expressed in placental tissue at comparable or greater levels than that in adipose tissue. The placentas of the small for gestational age (SGA) neonates expressed leptin mRNA and protein at significantly lower levels than those of the appropriate for gestational age (AGA) neonates (P=0.0034 and 0.0076), while the placentas of the large for gestational age (LGA) neonates expressed leptin mRNA and protein at significantly higher levels than those of the AGA neonates (P=0.043 and 0.021). Linear regression analysis showed placental ob gene transcription and leptin translation correlated significantly with cord leptin (r=0.39 and 0.43), and neonatal Ponderal Index (r=0.66 and 0.69). Conclusion　The placenta provides a source of leptin for the growing fetus, and this placental leptin might be a growth factor in intrauterine fetal development.