Analysis of fetal heart rate on-line at 32 weeks gestation.

Antenatal fetal heart rate (FHR) patterns were screened in 634 women with singleton pregnancies at 32 weeks gestation using a microprocessor on-line. The duration of the record was adjusted according to its character, varying from 10 min with high FHR variation (39% of records) to 45 min with low variation (4.7%). The average duration was 16.7 min. Of the 30 fetuses with the lowest FHR variation (less than 5th centile), 19 (63%) had a normal outcome. Of the 11 with an abnormal outcome five were born greater than or equal to 38 weeks; six were born by caesarean section at 32-34 weeks, resulting in an increased incidence in the group. Analysis of the numbers of accelerations, of decelerations, of episodes of high FHR variation or of fetal movements did not improve long-term prediction. It was concluded first, that antenatal FHR monitoring for up to 45 min at 32 weeks gestation had no long-term predictive value; and second, that 3% of our obstetric population have unreactive FHR traces at this age, with a normal outcome. This does not imply that consecutive antenatal records on the same high-risk patient at short intervals are not valuable clinically.