As an effective analgesic method,intrathecal analgesia has been widely accepted.Though labor analgesia could relieve the labor pain,it remains controversial about its adverse effects on labor progress and delivery outcomes.With the development of labor analgesia technique,a large number of clinical studies have suggested that the protocol,dosage and analgesic methods of local anesthesia may also affect the labor and delivery outcomes.There is a growing need to explore more optimized anesthetics and analgesic methods for clinical and scientific research.

Objective To assess the influences of early implementation of patient-controlled epidural analgesia (PCEA) in labor on uterine myoelectrical activity and delivery outcomes. Methods A prospective study was conducted on 240 singleton cephalic primiparae with spontaneous labor at Guangzhou Women and Children's Medical Center from January 2015 to October 2018. Those women, who were ready to accept PCEA, were randomly assigned to early- or late-PCEA group based on cervical dilation of 0-3 cm or 3-6 cm at the time of commencing PCEA, while those who refused PCEA in labor were classified as non-PCEA group. Uterine electromyographic activity and visual analogue score (VAS)were recorded before and 1 h and 2 h after PCEA. Patient satisfaction with labor, duration of the first stage of labor, volume of postpartum bleeding within 2 h after delivery and neonatal Apgar score were compared between different groups using multivariate analysis of variance, repeated measures analysis of variance, LSD-t test or Chi-square test. Results The VAS values 1 h after PCEA in the early- and late-PCEA group were both lower than that in the non-PCEA group (2.08±1.34 and 2.00±1.28 vs 7.65±1.04, LSD-t were － 27.713 and － 27.663, P<0.001) and those before PCEA (7.65±0.91 and 7.62±0.86, LSD-t were －32.879 and －33.349, P<0.001). The VAS values 2 h after PCEA in the early- and late-PCEA group were both lower than that in the non-PCEA group (1.63±1.53 and 1.41±1.56 vs 7.66±0.87, LSD-t were －27.018 and －27.823, P<0.001) and those before PCEA (LSD-t were －31.379 and －32.718, P<0.001).The patient satisfaction rate with labor was higher in the early-PCEA group comparing to the late-PCEA group [80.0% (72/90) vs 61.1% (55/90), P<0.001], and the two figures above were both higher than that of the non-PCEA group [20.0% (12/60), both P<0.001]. There was no significant difference in the duration of the first stage of labor, the volume of postpartum blood loss 2 h after delivery, oxytocin usage rate, the rate of convertion to cesarean section, neonatal birth weight or Apgar score at 1 or 5 min among the three groups (all P>0.05). There was also no significant difference in uterine electromyographic parameters among the three groups before or 2 h after PCEA (all P>0.05). The number and duration of burst, power density spectrum peak frequency, root mean square and total power 1 h after PCEA in the early- and later-PCEA group were all lower than those in the non-PCEA group [4.80±2.49 and 5.54±3.04 vs 9.67±2.44; (34.41±1.21) and (36.94±1.18) vs (41.68±1.53) s; (0.36±0.08) and (0.36±0.07) vs (0.48±0.05) Hz ; (0.05±0.04) and (0.05±0.05) vs (0.07±0.05) mV; (4.33±0.51) and (5.36 ±0.59) vs (9.90±1.43) pV2; all P<0.05]. Conclusions The effect of PCEA on uterine myoelectrical activity has no association with the commencing time. While early PCEA could alleviate the labor pain as soon as possible, which enable us to improve the efficacy of labor analgesia, patient satisfaction and maternal and neonatal safety without increasing cesarean section rate.