Background: The positive relationship between fat mass, bone mass and leptin has been shown in fetal mouse cartilage/bone. It has been shown that umbilical venous leptin predicts both the size of the neonatal skeleton and its estimated volumetric mineral density. Aims: This study investigates how birth weight and bone mineralization correlate with leptin levels. In addition, we aimed to determine the predictive value of anthropometrics measurements and gender on variability in bone mineral status. Methods: Umbilical cord venous blood samples were obtained at the delivery from 100 term newborn infants. Forty of the newborn infants had birth weights appropriate for gestational age (AGA), 30 were small for gestational age (SGA) and 30 were large for gestational age (LGA). Data were acquired using the whole body dual energy X-ray obsorptiometry scanner in the first 24 h after birth. Results: Leptin concentrations were higher in LGA (36.6 +/- 12.0 ng/ml; p < 0.0001), but lower in SGA (11.7 +/- 5.6 ng/ml; p < 0.001) than in AGA infants (20.3 +/- 7.6 ng/ml). Whole body bone mineral density and whole body bone mineral content were higher in LGA babies (0.442 +/- 0.025 g/cm(2), 71.6 +/- 9.0 g, p < 0.01, p < 0.001, respectively) but lower in SGA (0.381 +/- 0.027 g/cm(2), 29.1 +/- 9.1 g, p < 0.001, p < 0.001, respectively) than in AGA babies (0.426 +/- 0.022 g/cm(2), 53.7 +/- 9.6 g, respectively). The percentage of whole body bone mineral content was lower in SGA (1.3 +/- 0.3) than in AGA (1.6 +/- 0.2, p < 0.001) and LGA (1.7 +/- 0.2, p < 0.001). In stepwise linear regression analyses models; leptin is not found related to the bone indices. Conclusion: Our study does not provide support for the hypothesis that leptin may play a major role in the regulation of bone metabolism in the developing skeleton. Copyright (c) 2007 S. Karger AG, Basel.