Abdominal electromyography in laboring and non-laboring pregnant women at term and its clinical implications

To determine the patterns of uterine action potentials in laboring and non-laboring women at term using the non-invasive abdominal electromyography technique.

One hundred pregnant women at term who fulfilled the inclusion criteria were enrolled in the study and equally divided into two groups. Group I consisted of 50 women in active labor, while group II included 50 women not in labor. After enrollment, the cardiotocograph was applied to all women. Abdominal electromyographic recording was started and for every burst of action potential, we measured the amplitude, frequency and duration of action potential. The results were tabulated and statistically analyzed.

Both groups were comparable in demographic characteristics. Four patterns of EMG were detected. The amplitude of action potentials was significantly higher in laboring compared to non-laboring women (77.44 ± 11.25 vs 13.71 ± 8.57, P < 0.001). Similar significantly longer durations of electrical bursts were also noted in laboring women (45.94 ± 8.77 vs 7.11 ± 4.68 s, P < 0.001). Specific electromyographic changes were noted in women passing from the non-laboring to laboring state and in women who required oxytocin augmentation during labor.

Abdominal electromyography may help to distinguish between women in true active labor from those who are not. It also may help to identify women who will enter into labor within 24-72 h and those who require augmentation of labor.