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Compared with a standard dose of oxytocin, higher doses were not effective in reducing the rate of cesarean section births in a randomized trial.

Around 14.5% of nulliparous women who received high-dose oxytocin (6 mU/min) had a C-section delivery versus 14.4% who received the standard regimen (2 mU/min), a result that was not statistically significant, according to Moeun Son, MD, MSCI, of the Yale School of Medicine in New Haven, Connecticut, and colleagues.

However, patients in the high-dose group had a significantly shorter delivery time compared with those who received the standard dose (9.1 vs 10.5 hours, respectively), Son said in a presentation at the Society of Maternal-Fetal Medicine virtual meeting.

Researchers also found that a higher dose of oxytocin was associated with a lower risk of chorioamnionitis (relative risk 0.67, 95% CI 0.48-0.92).

"In this trial of nulliparas who received oxytocin for labor augmentation, high-dose oxytocin regimen did not significantly reduce the incidence of cesarean delivery when compared to standard dosing," Son said. "However, we found a shorter time to delivery, and evidence suggesting lower maternal and perinatal complications in the high-dose oxytocin group," adding that this evidence shows that a high-dose oxytocin regimen is safe, and may be preferred in this patient population.

Currently, there is no "gold-standard protocol" for oxytocin infusion, Son said. While a published reported a reduction in C-section births and shorter time to delivery with high-dose oxytocin regimens, the evidence was not strong enough to support routine use.

Son and colleagues investigated whether a high-dose oxytocin regimen for labor augmentation would result in a lower risk of C-section delivery for nulliparous women. They assigned participants 1:1 to standard or high-dose oxytocin.

The trial was conducted at Northwestern Memorial Hospital in Chicago from September 2015 to September 2020, and included first-time mothers with singleton pregnancies of at least 36 weeks. All participants of the study were determined to need oxytocin by their provider, and had a spontaneous labor. Participants were excluded if they received cervical ripening, Son noted.

Son's group included 1,003 pregnant women in the trial. The average maternal age was around 32 in both the high- and standard-dose groups, and the majority of trial participants were white. Researchers observed no significant differences in maternal age, self-reported race and ethnicity, marital status, or insurance type.

They also found no significant differences between the two groups in the maternal outcomes of postpartum endometritis and postpartum hemorrhage. Additionally, they did not observe higher risk of adverse neonatal outcomes in the high-dose group.

Son stated that the incidence of C-section delivery was lower than the estimated baseline incidence, and that the study may have been underpowered which limited the findings. Additionally, the trial was conducted at a large academic hospital so the results may not be generalizable to all medical settings.

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