The effect of fetal head compression and fetal acidaemia during labour on human fetal cerebral function as measured by the fetal electroencephalogram.

We investigated the effect of head compression and acidaemia during labour in 25 African primigravidae. Evidence that head compression had occurred during labour was confirmed by both clinical and radiological means at the end of a trial of labour. No significant difference could be demonstrated in the quantity of fetal electroencephalogram (EEG) abnormality that occurred in the groups with marked head compression as compared to the groups without marked head compression. Deterioration in the fetal EEG to a flat record known as electrocerebral silence (ECS) was associated with the development of acidaemia. As fetal heart rate (FHR) decelerations appeared the percentage of ECS in the fetal EEG record increased significantly (P less than 0.05), and likewise, as fetal acidaemia developed a highly significant increase in ECS in the fetal EEG was demonstrated (P less than 0.001). We concluded that in the management of trial of labour there was no significant deleterious change in the fetal EEG as a result of head compression, unless fetal acidaemia supervened. However, in the majority of these cases a significant increase in ECS to more than 20 per cent occurred in association with only moderate acidaemia (pH 7.25 to 7.30).