Aims-To examine the relation between maternal body fat and fetal metabolism. Methods-In this observational study, cord blood samples were collected from 60 infants of healthy women for the measurement of insulin and C peptide concentrations. Maternal weight, height, body mass index (BMI) and body composition (skinfold thickness measurements and bioelectrical impedance) were assessed at 13-15 weeks of gestation. Twenty five of the volunteers agreed to have a 75 g oral glucose tolerance test at 28-31 weeks of gestation. Results-Positive correlations were observed with both cord insulin or C peptide concentrations and maternal early pregnancy BMI (r=0.44, p=0.002 and r=0.33, p=0.008, respectively). There was no significant correlation between cord insulin or C peptide concentrations and birthweight or birth weight centiles. Conclusion-Maternal BMI could be a predictor of fetal cord insulin concentration. (Arch Dis Child Fetal Neonatal Ed 1999;81:F122-F124)