Antepartum fetal heart rate pattern associated with major congenital malformations.

Antenatal fetal heart rate monitoring of 20 fetuses with major congenital malformations revealed loss of long-term variability in 11 (55%) and an isolated, abrupt-onset fetal heart rate deceleration in 13 (65%). In ten (50%), loss of variability coexisted with periodic fetal heart rate decelerations. These fetal heart rate changes were significantly more prevalent in the malformed group than in a control population. There was also a significantly increased incidence of fetal distress in labor and in the requirement for primary cesarean section delivery. Perinatal mortality was 75%, reflecting the lethal nature of the malformations. Loss of long-term fetal heart rate variability associated with isolated, abrupt occurrence of fetal heart rate deceleration should raise the possibility of congenital malformations in an apparently normal pregnancy.