Intra-uterine deaths after suspicious, uncertain and normal antenatal fetal heart rate monitoring.

Stressed and non-stressed antenatal fetal monitoring was carried out 9 520 times in 5 932 high-risk patients. Intra-uterine death occurred in 48 patients. In 19 patients the fetus died within 1 week of monitoring but before the onset of labour; the results of monitoring had been normal in 14 of these. Abruptio placentae was the cause of 6 of these deaths. Many of the other causes of intra-uterine death were also acute complications such as haemorrhage due to placenta praevia, amniotic fluid infection, and cord prolapse. True false-negative test results were rare, and were seen most often in patients with preeclampsia, diabetes and haemolytic disease. Twin pregnancies also caused a problem, as double recording of the heart rate of the normal fetus could create a false sense of security.