Background: Monitoring uterine contractions by internal tocodynamometry is advised by the American Congress of Obstetricians and Gynecologists in certain situations (e.g., maternal obesity, when one-on-one nursing care is not available, when response to oxytocin [Pitocin] is limited). However, this recommendation is based on expert opinion, and several small trials have not shown reductions in adverse neonatal outcomes or in operative delivery rates with internal versus external monitoring. Bakker and colleagues conducted a randomized, multicenter clinical trial to determine if using an intrauterine pressure catheter during labor would lead to better outcomes than those associated with external monitoring.

The Study: The authors randomized 1,456 women to receive internal or external monitoring of uterine activity during labor. All participants had a singleton pregnancy in cephalic position with a gestational age of more than 36 weeks and an indication for induction or augmentation of labor. Patients were excluded if they had a uterine scar, were positive for hepatitis B or human immunodeficiency virus infection, or had signs of an intrauterine infection or fetal distress. The use of intrauterine pressure catheters was allowed in the external monitoring group if there were insufficient uterine contractions, if cervical progression had been absent for two hours, or if cesarean delivery was being considered.

Results: No significant difference was noted in operative delivery rates between the groups (31.3 and 29.6 percent in the internal and external monitoring groups, respectively). The groups also were similar in the time to delivery and in antibiotic and analgesic use. Adverse neonatal outcomes (e.g., Apgar scores of less than 7 at five minutes, umbilical artery pH scores of less than 7.05, neonatal admission to the hospital for more than 48 hours) were equivalent between the groups. Post hoc analyses showed no notable interactions between monitoring type and the type of labor (induced versus augmented), body mass index (30 kg per m² or less versus more than 30 kg per m²), or parity (primiparous versus multiparous) with regard to adverse neonatal outcomes or the need for operative delivery.

Conclusion: The authors conclude that compared with external monitoring of uterine activity in women with induced or augmented labor, internal tocodynamometry does not improve the rates of operative delivery or adverse neonatal outcomes.