Association of Labor Epidural Analgesia with Neonatal Umbilical Arterial Blood pH and Apgar Score: The Japan Environment and Children’s Study (JECS)

Background: Labor epidural analgesia is recognized worldwide as the gold standard for maternal pain relief during delivery and has been increasingly used in Japan. However, studies on labor analgesia in Japan are scarce, and evaluation of neonatal outcomes associated with this procedure remains limited. Among the key aspects in the safety evaluation of labor epidural analgesia are the potential effects on neonatal umbilical arterial blood pH (UmA-pH) and Apgar score. Therefore, we determined whether labor epidural analgesia during vaginal delivery is associated with neonatal UmA-pH and Apgar score among women delivering in Japan. Methods: In this birth cohort study, we prospectively analyzed data collected from the Japan Environment and Children's Study (JECS). We included Japanese pregnant women who had singleton vaginal deliveries. The primary exposure was labor epidural analgesia, and the primary outcomes were UmA-pH and Apgar score at 1 and 5 min following birth. Multivariate logistic regression was employed to examine the associations between labor epidural analgesia and neonatal outcomes, with adjustment for potential confounders. Adjusted odds ratios (aOR) and 95% confidence intervals (CIs) were reported. Furthermore, a sensitivity analysis using stabilized inverse probability of treatment weighting (IPTW) was conducted. Results: Of the 96,443 women who had singleton deliveries in the JECS, 55,227 were included in the final analysis, 1,311 (2.4%) of whom received labor epidural analgesia. In the multivariate logistic regression analysis, a statistically significant association was observed between labor epidural analgesia and a 1-min Apgar score < 7 (aOR: 1.54; 95% CI: 1.03-2.29). However, only one neonate in the labor epidural analgesia group had a 5-min Apgar score < 7. Moreover, no significant association was observed between labor epidural analgesia and UmA-pH < 7.2 (aOR: 0.94; 95% CI: 0.76-1.17). In the IPTW-based sensitivity analysis, the effect estimates were consistent in direction with the primary analysis, supporting the robustness of the main findings. Conclusion: In this large cohort of singleton vaginal births in Japan, the use of labor epidural analgesia had little to no clinically meaningful effect on neonatal outcomes, including UmA-pH < 7.2 and Apgar score < 7. These findings support informed decision-making for pregnant women in Japan who are considering labor epidural analgesia.