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Labor

Poster Session 2

(457) Etiology of abnormal labor progress among patients with obesity: is it contraction strength?

Tuesday, February 13, 2024
3:30 PM – 5:00 PM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level
Foundation Awardee
Objective: Over 35% of reproductive-age women in the US are obese and at risk for obstetric complications due to abnormal labor and cesarean delivery. However, there is a limited understanding of why and how obesity leads to abnormal labor.  The objective of this prospective study was to compare uterine contractility characteristics, collected via universal intrauterine pressure catheters (IUPC), between patients with and without obesity.

Study Design: This was a prospective cohort study of women with a singleton gestation admitted for labor at ≥37 weeks gestation. Upon amniotomy, all participants had an IUPC placed. The primary outcomes were four parameters of uterine contractility: frequency, peak pressure, duration, and force (Montevideo units, MVU). Secondary outcomes were intrauterine resting tone and presence of tachysystole. Outcomes were compared between patients with and without obesity (BMI ≥ 30 kg/m2) at four time points: upon amniotomy and IUPC placement, at active labor (defined as first cervical exam ≥6 cm), at maximum oxytocin dose, and in the 1 hour prior to full cervical dilation. Sub-group analyses were performed among women with vaginal delivery and women receiving oxytocin.

Results: Of the 224 participants in this study, 118 (52.7%) had obesity. Women with obesity were more likely to be induced (97.5 vs 81.1%, p< 0.01). Majority of the cohort, 88.0%, had a vaginal delivery and this did not statistically differ between patients with or without obesity. There were no differences in contraction peak pressure, frequency, duration or force between patients with and without obesity at any of the four time points evaluated. Patients with obesity had higher average resting tone (22.3 vs 19.6 mmHg, P< 0.01). There were no differences in occurrence of tachysystole between the groups.

Conclusion: Women with obesity were able to achieve similar contraction characteristics associated with frequency and strength as patients without obesity. Differences in uterine contraction pressure and frequency may not explain the disparate rates of labor dystocia and cesarean rates among women with obesity.