Does artificial rupturing of membranes in the active phase of labor enhance myometrial electrical activity?

To determine whether artificial rupture of membranes (AROM) during active phase of labor augments uterine contractility using Electrical Uterine Myography (EUM).

A prospective study of 31 women with term singleton pregnancy during active phase of labor. Using a non-invasive EUM technique, electrical uterine activity was recorded in the 30 min preceding AROM and in the immediate 30 min thereafter. Augmentation was defined as >5% increase in EUM index between the basal and post-AROM states, representing the mean EUM increase of the entire cohort. Low basal uterine contraction was defined as EUM index of less than the entire cohort median result prior AROM (3.5 micro-Watt-Second (mWS)).

Mean dilatation in which AROM was preformed was 5.5 ± 1.8 cm. There was a significant increase in mean EUM measurement in the post-AROM compared to the basal state (3.59 ± 0.39 versus 3.42 ± 0.47 mWS, p < 0.001). In multivariate analysis, low BMI and low basal uterine contractions were the only significant predictors for augmentation following AROM (OR 0.69, 95% C.I 0.45-0.97, p = 0.009 and OR 16.03, 95% CI 1.90-134.69, p = 0.003, respectively).

Myometrial electrical activity was significantly enhanced following AROM. Augmentation was mostly pronounced in patients with lower BMI and initial lower basal uterine contraction.