Effect of Pethidine Injection on the Duration of Labor and Pregnancy Outcomes: A Retrospective Cohort Study

Background and Objectives: Long and ineffective labor causes hardships for mothers and doctors and increases the rate of cesarean sections and medical comorbidities. Several factors contribute to effective and less painful labor, including maternal age, parity, fetal characteristics, and the medications or procedures that obstetricians use for labor. We aimed to study the factors that affect labor duration and identify those that make labor more effective. Materials and Methods: This retrospective study included 141 patients who underwent normal vaginal deliveries at the Daegu Catholic University Medical Center between April 2013 and April 2022. Among the 141 patients, 44 received pethidine intravenously, 88 received oxytocin intravenously, and 64 received epidural anesthesia. The duration of the active phase and second stage of labor were recorded according to the findings of a manual examination of the cervix and continuous external electronic monitoring. We analyzed maternal and neonatal medical records and performed binomial logistic regression to identify the factors associated with a shorter active phase of labor. The clinical outcomes in mothers and neonates were also evaluated. Results: Among the various clinical factors, multiparity (odds ratio of parity 0.325) and the use of pethidine (odds ratio 2.906) were significantly associated with shortening the active phase of labor to less than 60 min. The use of epidural anesthesia or oxytocin was not significantly associated with reducing the active phase of labor. When patients were divided into two groups based on whether a pethidine injection had been used during labor, the duration of the active phase was shorter in the pethidine injection group than in the control group for both nulliparas and multiparas. No significant differences in the duration of the second stage of labor were observed between the pethidine injection and control groups. There were no significant differences in pregnancy outcomes, including the need for mechanical ventilation of neonates, Apgar scores, neonatal intensive care unit admissions, number of precipitous deliveries, maternal adverse side effects of drugs, or duration of maternal hospitalization between the two groups. Conclusions: Pethidine can be safely administered to women during labor to help reduce the duration of the active phase by promoting dilatation of the cervix and preventing complications that may result from prolonged labor. Pethidine may be helpful, especially for those who cannot receive epidural anesthesia or who cannot afford it. However, large-scale randomized controlled studies are required to evaluate the efficacy and safety of this drug during labor. Furthermore, it would be helpful if various studies were conducted depending on the timing of administration and indications for delivery.