Fetal heart rate and intrauterine growth.

To assess whether fetal heart rate in early and late pregnancy relates to size at birth. Prospective study of fetal heart rates in early and late pregnancy. Princess Anne Hospital, Southampton. 63 primigravid women. Anthropometric measurements made on the newborn infant. There were no differences in heart rate between the sexes at 18 weeks gestation but by 36 weeks the boys had rates which were 4.4 beats lower than those of the girls. Higher fetal heart rate at 18 weeks was associated with lower ponderal index, smaller head circumference and smaller mid-arm circumference. There were no trends in fetal heart rate at 36 weeks with any birth measurements. Babies born at term who have a pattern of neonatal measurements which reflect growth retardation have raised heart rates in early pregnancy. Influences which impair fetal growth appear to take effect early in gestation.