Occurrence of ST-changes recorded with the STAN® S21-monitor during normal and abnormal fetal heart rate patterns during labour

ObjectiveTo determine the frequency of ST-changes in the fetal electrocardiogram (ECG) both during normal and abnormal fetal heart (FHR) traces and to study relations with characteristics of pregnancy and delivery.Study designRetrospective analysis of 563 FHR + ECG-recordings. ST-changes were counted for all recordings with respect to their FHR pattern. Relationships between the occurrence of ST-events and characteristics of pregnancy and delivery were determined for the recordings with a completely normal FHR tracing during the first stage.ResultsST-events were present during 51.7% of recordings in the first stage of labour and during 24.3% of the recordings in the second stage. Surprisingly, events occurred during the first stage at a similar incidence during normal and abnormal FHR-patterns. During the second stage of labour events also occurred in a similar percentage of normal, intermediary and abnormal recordings, but – if present – events were more numerous during the abnormal FHR traces. In the subgroup of cases with a normal FHR pattern more events per hour occurred in babies born at 36–37 weeks of gestation and in boys.ConclusionST-events are a frequent finding during normal FHR tracings.