['To study the role of placental leptin in intrauterine cord leptin production and its relationship with neonatal anthropometry.', 'Forty women and their babies were enrolled and approved by Xinhua Hospital (Shanghai, China) and Jiangbei Hospital (Nanjing, China) in this study. Placental tissue was assayed for leptin mRNA by reverse transcription/polymerase chain reaction (RT/PCR), and assayed for ob 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.', 'Ob gene was expressed in placental tissue at comparable or greater levels than that in adipose tissue. Comparison of the relative levels of leptin to beta-actin mRNA by multiplex RT/PCR revealed that the placenta of the small for gestational age (SGA) neonates expressed leptin mRNA at significantly lower levels 0.61 +/- 0.15 than that of the appropriate for gestational age (AGA) neonates 0.83 +/- 0.20 (P = 0.0034), while the placenta of the large for gestational age (LGA) neonates expressed leptin mRNA at significantly higher levels 1.00 +/- 0.23 than that of the AGA neonates (P = 0.043). Immunohistochemical techniques showed the immunostaining pattern in the cytoplasm of trophoblastic cells. Western-blot showed that the placenta of the SGA neonates expressed leptin at significantly lower levels 0.26 +/- 0.05 ng/mg than that of the AGA neonates 0.34 +/- 0.09 ng/mg (P = 0.007 6), while the placenta of the LGA neonates expressed leptin at significantly higher levels 0.43 +/- 0.10 ng/mg than that of the AGA neonates (P = 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).'] Does [ Placental leptin correlate with intrauterine fetal growth and development ]?