Uterine electrical activity at labor: Is there a correlation between labor stages?

Objective: To determine the association between the myometrial electrical activity in the active and second stages of labor at term using electrical uterine myography (EUM). Methods: A prospective observational study of 47 singleton deliveries at term in a tertiary hospital. All women were assessed using noninvasive 9-channel surface electrodes of the EUM during labor. EUM index (EUMi) was calculated as the mean electrical activity during a 30 min monitoring period and expressed as microjouls (MJ). Mean EUMi of the active and second stages of labor were compared accordingly. Results: Mean EUMi during the active phase was 3.53 ± 0.43 MJ, whereas mean EUMi in the second stage was 3.66 ± 0.48 MJ (p = 0.02). Correlation analysis between mean EUMi of the active and second stages of labor produced r² = 0.68 (p < 0.01). In a regression analysis model EUMi of the active stage of labor remained strongly correlated with the duration of the second stage (r2 = 0.73, p < 0.001). No correlation was found between EUMi and the duration of the second stage. Conclusion: A positive correlation of myometrial electrical activity exists between active phase and second stage of labor. However, while EUMi was associated with the duration of the active phase, no correlation was found between EUMi and the duration of the second stage.