High oxytocin dose helps reduce postpartum haemorrhage

Use of high-dose oxytocin postpartum appears to result in reduced rates of postpartum haemorrhage (PPH) when compared with traditional doses, as shown in a study presented at SMFM 2024.

“The most effective dose of prophylactic oxytocin for the prevention of PPH is unknown,” said the researchers led by Ashley E Shea from the University of Alabama at Birmingham, Alabama, US. “Our objective was to compare rates of PPH and the need for additional PPH interventions between postpartum high dose and lower dose oxytocin regimens.”

Shea and her team performed a secondary analysis of a multicentre randomized controlled trial (RCT) of nulliparous women between May 2014 and December 2017 with term singleton pregnancies. The trial examined immediate versus delayed pushing in women in the second stage.

The research team ascertained postpartum oxytocin from each of the six participating centres and categorized this as either high dose (80 units per 500 mL over 1 hour after placental delivery) or lower dose (10‒30 units per 500‒1,000 mL over 1‒4 hours).

A composite of uterotonic use, any blood transfusion, and PPH served as the primary outcome, while individual composite components were secondary. Shea and colleagues compared these outcomes between groups. They also estimated adjusted odds ratio and 95 percent confidence intervals [CIs] using logistic regression, with the lower dose group as the reference.

A total of 2,404 patients from the primary RCT were included in the analysis. Of these, 455 (19 percent) were in the high-dose group and 1,949 (81 percent) in the lower-dose group. Women in the high-dose group tended to be younger, African American, obese, have magnesium sulfate exposure, and achieve vaginal delivery. [SMFM 2024, abstract 7]

Patients who received high-dose oxytocin achieved an almost 50-percent decrease in the likelihood of the primary composite outcome compared to those who received a lower dose (adjusted odds ratio [aOR], 0.53, 95 percent CI, 0.34‒0.82). This was primarily driven by >50-percent reduced odds of PPH (aOR, 0.44, 95 percent CI, 0.27‒0.72).

Secondary outcomes

Likewise, the frequencies of secondary outcomes were much lower in the high-dose group, but no differences were seen in the odds of these outcomes following multivariable adjustment. In stratified analysis, low (10‒20 units), moderate (30 units), and high doses (80 units) showed similar results.

“High-dose PP oxytocin was associated with lower rates of PPH than traditional oxytocin doses,” the researchers said. “Future multicentre trials of postpartum oxytocin dose should be performed to improve outcomes.”

In a recent study, increasing duration and total dosage of oxytocin augmentation modestly increased the likelihood of PPH and estimated blood loss. [Am J Obstet Gynecol 2024;230:247.E1-247.E9]

“However, in comparison with women for whom oxytocin was not used and after controlling for potential confounders, there was no clinically significant association between oxytocin use for augmentation and estimated blood loss or the risk of PPH,” according to the investigators.