Prolonged Oxytocin Exposure for Labor Induction Linked to Bleeding Risk

Prolonged exposure to oxytocin during birth was associated with an increased risk for obstetric hemorrhage, according to a retrospective cohort study.

Among over 2,200 patients who received intrapartum oxytocin for labor induction or augmentation, those who were exposed for 12 or more hours had a 52% increased risk of obstetric hemorrhage (adjusted odds ratio [aOR] 1.52, 95% CI 1.21-1.91) compared with those who were exposed for less than 12 hours, reported Megan Alexander, MS, of Boston University School of Medicine.

In addition, those with this prolonged exposure had a 26% greater mean quantitative blood loss (P<0.001), noted Alexander during a presentation at the American College of Obstetricians and Gynecologists (ACOG) annual meeting, held in San Diego.

Oxytocin exposure for 12 or more hours was not associated with an increased risk of hemorrhage-related morbidity, the study found.

Co-investigator Ashley Comfort, MD, of Boston Medical Center, said it was significant that patients who had a longer exposure to oxytocin and went on to have a C-section did not face an increased hemorrhage risk. In the context of high rates of C-section deliveries, as well as an effort to decrease these rates, more data on the risk of obstetric interventions by mode of delivery is critical to help clinicians make informed choices.

"There are risks and benefits of each clinical decision that we make," Comfort told MedPage Today. "I think it's important to make sure that we have really good evidence to support our clinical decisions, so that we can better serve our patients."

Obstetric hemorrhage is a preventable, but common, cause of maternal morbidity and mortality, Comfort said.

The relationship between intrapartum oxytocin exposure and obstetric hemorrhage is not completely understood, and previous studies have been limited by their use of estimated, as opposed to qualitative, blood loss data, Alexander noted.

For this retrospective cohort analysis, the researchers aimed to evaluate whether prolonged exposure to oxytocin was associated with increases in quantitative blood loss, obstetric hemorrhage, or hemorrhage-related maternal morbidity.

Of 5,332 patients delivering at Boston Medical Center from January 2018 through December 2019, 2,232 (41.9%) were exposed to intrapartum exogenous oxytocin for labor induction or augmentation. Women were categorized by the amount of time they were exposed to oxytocin: less than 12 hours or 12 hours or more.

The researchers also analyzed all outcomes by mode of delivery. Among all vaginal deliveries, patients exposed to 12 or more hours of intrapartum oxytocin had a 21% greater mean quantitative blood loss than those who had a shorter exposure (P<0.001), as well as a 47% increased risk of obstetric hemorrhage (aOR 1.47, 95% CI 1.03-2.11). There were no significant differences among cesarean deliveries.

Future research should aim to explore the impact of rate and dose of oxytocin on hemorrhage risk, the investigators concluded.

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