Antenatal origins of individual differences in heart rate.

This study examines prenatal-to-postnatal stability in heart rate and variability from mid-gestation through the first year of life. Fetal heart rate data were collected from 52 healthy fetuses at 24, 30, and 36 weeks gestation, and again at 2 weeks and 12 months of age. Fetal heart rate measures were stable during gestation and positively associated with neonatal and infant measures. Maternal pulse rate and oxygen saturation were moderately associated with fetal heart rate. Together, fetal cardiac (heart rate and variability) and maternal physiologic measures (blood pressure and oxygen saturation) explained 40 and 48% of the variance in heart rate and variability, respectively, at 1 year of age. These common measures of individual differences in autonomic function are enduring characteristics that originate during fetal development. Copyright 2000 John Wiley & Sons, Inc.