Changes in cervical electromyographic activity and their correlation with the cervical response to myometrial activity during labour.

Intrauterine pressure, cervical dilatation and cervical electromyographic activity were recorded synchronously in five women from induction through the latent phase of labour and into the active phase. In all cases the electromyographic activity recorded in early labour was grouped into bursts synchronised with uterine and cervical contractions. Between these increases in electromyographic activity a significant background level of electrical activity was present in each case. With effacement the amount of electrical activity from the cervix was reduced, although increases in activity were noted to be synchronous with myometrial activity and, at this stage, dilatation of the cervix. This type of activity was typical of the active phase of labour until full dilatation, whilst the previous pattern typified the latent phase. The implications of these findings for the function of the cervix and the mechanism of cervical effacement are discussed.