Labor and delivery outcomes with remifentanil patient-controlled analgesia versus labor epidural analgesia among women with and without obesity: a retrospective population-based cohort study (2015-2024).

BACKGROUND: Evidence regarding the safety and effectiveness of intravenous remifentanil patient-controlled analgesia (PCA) in women with obesity remains limited. We compared labor and delivery outcomes associated with remifentnail PCA and labor epidural analgesia according to maternal body mass index. METHODS: This retrospective population-based cohort study included women with singleton, term, cephalic pregnancies undergoing spontaneous or induced labor who received either remifentanil PCA or labor epidural analgesia in Slovenia between 2015 and 2024. Analyses were performed separately in women with body mass index < 30 kg/m2 and ≥ 30 kg/m2. Multivariable logistic regression was used to adjust for relevant maternal and obstetric confounders. Primary outcomes were intrapartum cesarean delivery and operative vaginal delivery. RESULTS: A total of 52,118 women were included, of whom 46,448 with body mass index < 30 kg/m2 and 5670 with body mass index ≥ 30 kg/m2. Remifentanil PCA was associated with lower risks of intrapartum cesarean delivery and operative vaginal delivery than labor epidural analgesia in both body mass index strata (all P ≤ 0.001). In contrast, remifentanil PCA was associated with higher risks of postpartum hemorrhage across both body mass index groups, and among women with body mass index < 30 kg/m2, higher risks of blood transfusion and third- or fourth-degree perineal tears. Neonatal outcomes were otherwise comparable between groups. In women with body mass index < 30 kg/m2, remifentanil PCA was associated with lower odds of an Apgar score < 7 at 1 min, although no differences were observed at 5 min, in neonatal intensive care unit admission, or in perinatal asphyxia. CONCLUSIONS: In this large population-based cohort study, remifentanil PCA was associated with lower risks of intrapartum cesarean delivery and operative vaginal delivery than labor epidural irrespective of maternal body mass index, without evidence of increased neonatal morbidity. These findings, derived from an observational study, should be interpreted cautiously given the potential for residual confounding and selection bias, and further prospective studies are required to clarify the causal relationships between analgesic technique and labor outcomes.