Figure 1. Uterine activity and amniotic fluid pressure before and during labour.

Uterine electromyogram (EMG_u) and amniotic fluid pressure (P_AF) from a fetus taken before labour (pre-labour), during early labour and in advanced labour. Before the establishment of labour, infrequent uterine contractions gave rise to a small increase in amniotic fluid pressure. In early labour, uterine contractions were more frequent and powerful, while in advanced labour maternal pushing was evident and it was sometimes in phase with the EMG_u as shown in this record.