Intramyometrial injection versus intravenous infusion of oxytocin for maintaining uterine contractility during elective caesarean delivery in a randomised controlled trial

Oxytocin is commonly administered during caesarean delivery (CD) to prevent postpartum haemorrhage as an initial bolus followed by a maintenance dose. Nearly half of perinatal centres in Japan utilise intramyometrial (IMY) oxytocin. IMY oxytocin is less effective than intravenous (IV) oxytocin as the initial dose for inducing uterine contractions. However, its role as a maintenance dose remains unclear. We evaluated the efficacy of IMY oxytocin versus continuous IV infusion for maintaining uterine contractility during elective CD. Twenty-two women undergoing elective CD were randomised to receive an initial IV bolus of 1 IU of oxytocin, followed by either 5 IU IMY oxytocin or a continuous IV infusion of 5 IU oxytocin. Total blood loss, along with haemodynamic parameters, was assessed. No significant difference in total blood loss was observed between the IMY and IV groups (median 634 mL [540-718] vs. 642 mL [507.5-706.5], P = 0.66). Conversely, IMY oxytocin resulted in smaller reductions in blood pressure and lower phenylephrine requirements after delivery. While IMY oxytocin did not significantly reduce total blood loss compared with continuous IV infusion, it was associated with better haemodynamic stability. Further studies are required to confirm these findings.Clinical trial registration: Japan Registry of Clinical Trials, jRCTs041210153, 25/04/2022.