[en] Effects of low-level cadmium (Cd) exposure during early life on fetal growth remain unclear. Our aim was to evaluate whether Cd exposure in maternal urine and umbilical cord blood was associated with birth size parameters. A birth cohort study including 1073 mother-newborn pairs was conducted from 2009 to 2010 in an agricultural population in China. Cd concentrations were analyzed in both cord blood and maternal urine. Generalized linear models were performed to determine associations between maternal and neonatal exposure to Cd and birth indicators, including birth weight, length, head circumference and ponderal index. The median (25th to 75th percentile) value of Cd concentration in maternal urine and umbilical cord blood was 0.19 (0.08, 1.00) μg/L and 0.40 (< LOD ~ 0.62) μg/L, respectively. After adjusting for potential confounders, Cd concentration in cord blood was significantly negatively associated with ponderal index at birth [β = − 0.06 g/cm³, 95% confidence interval (CI): − 0.11, − 0.02; p < 0.01]. Considering sex difference, significant reduction in ponderal index was only observed in males (β = − 0.06 g/cm³, 95%CI: − 0.11, − 0.02; p < 0.01), but not in females (β = − 0.03 g/cm³, 95%CI: − 0.07, 0.01; p = 0.18) (p for interaction term = 0.24). Additionally, no significant associations were observed between maternal urinary Cd levels and birth outcomes. Our findings suggest that adverse effects of neonatal exposure to Cd on fetal growth are of considerable public health importance. - Highlights: • Cd concentrations were determined in both umbilical cord blood and maternal urine. • Associations between Cd exposure and birth outcomes were explored in 1073 mother-newborn pairs. • Cord blood Cd concentrations were negatively associated with ponderal index of neonates. • Adverse effects of Cd exposure on birth outcomes differed by neonatal sex.