Stability in cardiac indicators before birth and their utility in predicting variation in postnatal development were examined. Fetal heart rate and variability were measured longitudinally from 20 through 38 weeks gestation (n = 137) and again at age 2 (n = 79). Significant within-individual stability during the prenatal period and into childhood was demonstrated. Fetal heart rate variability at or after 28 weeks gestation and steeper developmental trajectories were significantly associated with mental and psychomotor development at 2 years (n = 82) and language ability at 2.5 years (n = 61). These data suggest that the foundations of individual differences in autonomic control originate during gestation and the developmental momentum of the fetal period continues after birth.