Antepartum measurement of the preejection period in high-risk pregnancy.

The preejection period (PEP) of the fetal heart was measured in the antepartum period in 32 high-risk patients between 32.5 and 42 weeks' gestation. Successful measurements were made 70% of the time using an abdominal electrocardiogram and a single-crystal Doppler ultrasound transducer with narrow band-pass amplifier. PEP was found to correlate directly with gestational age (GA) and inversely with fetal heart rate (FHR). Three of 4 growth-retarded infants and another infant who was asphyxiated at birth had significant shortening of PEP prior to delivery.