TOPLINE:

Elevated BMI was associated with greater oxytocin requirements during labor induction, but risks linked to higher dosing were attenuated among individuals with higher BMI. Individuals receiving maximum oxytocin doses exceeding 18 milliunits/min had elevated risk for cesarean delivery and postpartum hemorrhage, with stronger associations in those with normal weight than in those with obesity.

METHODOLOGY:

• Researchers conducted a retrospective cohort study of singleton births from January 1, 2013, through December 31, 2022, at a large tertiary hospital in New York City, that included 20,215 deliveries in individuals receiving oxytocin for labor induction.
• Delivery BMI was classified as normal weight (18.5-24.9), overweight (25.0-29.9), class I-II obesity (30.0-39.9), and class III obesity (≥ 40), with maximum oxytocin dose rate categorized into quartiles: quartile 1 (0-8 milliunits/min), quartile 2 (9-12 milliunits/min), quartile 3 (13-18 milliunits/min), and quartile 4 (> 18 milliunits/min).
• Primary outcomes were cesarean delivery and postpartum hemorrhage, identified if documented blood loss exceeded 1000 mL, receipt of blood products after delivery, or postpartum hemorrhage recorded in the delivery summary.
• Modified Poisson regression models stratified by BMI estimated risk ratios (RRs) for cesarean delivery and postpartum hemorrhage, with adjustment for oxytocin exposure duration, insurance, maternal age, parity, gestational comorbidities, cervical status, gestational age, fetal sex, and birth weight.
• Analysis included oxytocin dosing data obtained from the medication administration record, with maximum dose rate used as the primary exposure to isolate the association between oxytocin dose intensity and maternal outcomes independently of induction duration.

TAKEAWAY:

• Among 20,215 deliveries, 16.9% were to individuals with normal weight, 43.1% to those with overweight, 35.1% to those with class I-II obesity, and 4.9% to those with class III obesity, with maximum oxytocin dose and exposure duration increasing with BMI.
• Individuals in the highest oxytocin quartile (> 18 milliunits/min) had elevated risk for cesarean delivery compared with those in the lowest two quartiles, with an adjusted RR of 1.8 (95% CI, 1.5-2.2) for normal weight, 1.9 (95% CI, 1.7-2.1) for overweight, 1.8 (95% CI, 1.7-2.0) for class I-II obesity, and 1.2 (95% CI, 1.0-1.5) for class III obesity.
• Highest-quartile oxytocin dosing was associated with increased postpartum hemorrhage risk, with an adjusted RR of 3.0 (95% CI, 1.7-5.4) for normal weight, 1.4 (95% CI, 1.0-1.8) for overweight, and 1.6 (95% CI, 1.2-2.0) for any obesity class, demonstrating greater risk in individuals with normal weight than those with obesity.
• Third-quartile oxytocin dosing (13-18 milliunits/min) was not associated with increased risk for cesarean delivery or postpartum hemorrhage in individuals with overweight or obesity, suggesting a potential target dosing range for future safety and efficacy studies.

IN PRACTICE:

“Elevated BMI was associated with greater oxytocin requirements, but risks associated with increased dosing were attenuated in individuals with higher BMI. Tailored dosing strategies may improve labor efficacy and maternal safety,” the authors of the study wrote.

SOURCE:

The study was led by Rebecca M. Cohen, BSE, Icahn School of Medicine at Mount Sinai in New York City. It was published online in O&G Open.

LIMITATIONS:

The study was conducted within a single health system, which may limit generalizability to other settings with different induction protocols or patient populations. Potential residual confounding by cesarean delivery indication or PPH [postpartum hemorrhage] cause exists, as observed associations may reflect underlying patient characteristics prompting intervention rather than the effects of the intervention itself. The study lacked information on prior cesarean delivery, induction indication, cesarean delivery indication, PPH cause, uterine contractility, fetal tracing, a full range of maternal comorbidities, and newborn outcomes, which could influence the interpretation of findings. The analysis was restricted to deliveries with complete oxytocin dosing data and excluded those with missing or implausible values, potentially introducing selection bias.

DISCLOSURES:

This study received support in part through computational and data resources provided by Scientific Computing and Data at the Icahn School of Medicine at Mount Sinai, funded by the Clinical and Translational Science Award grant UL1TR004419 from the National Center for Advancing Translational Science. Kimberly B. Glazer, PhD, MPH, disclosed receiving support from a Career Development Award from the Agency for Healthcare Research and Quality (K01HS029525). Katharine J. McCarthy, PAP, MPH, disclosed receiving support from an R01 grant from the NIH, the National Heart, Lung, and Blood Institute (R01HL177524). The authors reported having no potential conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.