Neonatal head circumference and the treatment of maternal hypertension.

In a random controlled trial of methyldopa for the treatment of hypertension in pregnancy presenting before 28 weeks gestation, the newborn in the treated group had relatively smaller head circumferences. This difference persisted at two months of age when correction had been made for birth weight, gestation and sex, but was no longeer detectable at six or twelve months. Within the treated group no relationship was found between neonatal head circumference and the total amount or duration of methyldopa received during pregnancy. Comparison of treated and untreated groups according to the time of entry to the study showed that significant differences in neonatal head circumference were only present in patients who entered between 16 and 20 weeks gestation. It is possible that this could be a sensitive period for the interaction of fetal head growth and the onset of specific treatment in hypertensive pregnancy.