Effects of Patient-Controlled Epidural Analgesia on Uterine Electromyography During Spontaneous Onset of Labor in Term Nulliparous Women.

OBJECTIVE

To investigate the effect of patient-controlled epidural analgesia (PCEA) on uterine electromyography (EMG) activity in term pregnant women during labor.

METHODS

Nulliparous pregnant women in spontaneous term labor (N = 30) were enrolled (PCEA group, n = 20 and control group, n = 10). Five time periods (30 minutes each) were defined for noninvasive abdominal recordings and analysis of uterine EMG activity, that is, period I: before PCEA treatment with 2-cm cervical dilation; periods II to IV: each period successively at 30, 60, and 120 minutes after PCEA; and period V: second stage of labor with cervix at 10 cm dilation. Control patients without PCEA were monitored during the same times. The number of bursts/30 min, power density spectrum peak frequency, mean amplitude, and duration of uterine EMG bursts were measured to assess uterine EMG activity. Maternal, fetal, and labor characteristics were also recorded. Data were analyzed by analysis of variance followed by other tests.

RESULTS

Electromyography parameters are significantly lower (P < .001) after PCEA (periods II to IV) compared to controls but similar between groups by period V (P > .05). Also, patients with PCEA have a slower rate of cervical dilation (P < .003, period IV only) and longer labor in both stage 1 and stage 2 (P < .05). All patients have similar (P > .05) positive labor outcomes.

CONCLUSIONS

Patient-controlled epidural analgesia initially suppresses uterine EMG and slows cervical dilation thereby prolonging labor. However, the EMG activity recovers with labor progress with no effects on delivery outcomes.