Electromyographic observations on the human cervix during labor.

The activity of smooth muscles in the cervix is one of the relevant factors for its dilatation during labor, but in humans it has not yet been sufficiently studied. Muscular activity may be observed by measuring electromyographic phenomena. In 60 parturient women of different parity and with various degrees of cervical ripeness at the onset of labor, the cervical electromyographic activity was measured through the entire course of labor in synchronization with uterine pressure measurements and also in 30 cases in synchronization with measurements of the uterine corpus electromyographic activity. The conditions necessary for successful measurements are described. The intensity of the cervical electromyographic activity was found to decrease with the level of cervical ripeness and with parity. When measured in the longitudinal direction, the cervical electromyographic activity resembled that of the uterine corpus, but when picked up from the circular lead, in a few cases of unripe cervices it differed from the electromyographic activity of the uterine corpus.