(561) Effect of oxytocin rest on labor outcomes and uterine contractility during induction of labor

Thursday, January 30, 2025

4:00 PM – 6:00 PM

Submitting Author and Presenting Author(s)

McKenzie Barber, MD (she/her/hers)

Washington University in Saint Louis
St. Louis, MO, United States

Coauthor(s)

NR

Nandini Raghuraman, MD, MSCI

Assistant Professor of Ob&Gyn
Washington University School of Medicine in St. Louis
St. Louis, Missouri, United States
Katherine H. Bligard, MA, MD

Assistant Professor of Ob&Gyn
Washington University School of Medicine in St. Louis
St. Louis, Missouri, United States
Jeannie C. Kelly, MD, MS (she/her/hers)

Associate Professor
Washington University School of Medicine in St. Louis
St. Louis, Missouri, United States
Antonina I. Frolova, MD, PhD (she/her/hers)

Assistant Professor of Ob&Gyn
Washington University School of Medicine
St. Louis, Missouri, United States

Objective: For patients with inadequate contractions despite high-dose continuous oxytocin (OT), a period of OT rest is often trialed to resensitize uterine smooth muscle to OT; however, the utility of this is unknown. Our aim was to determine the effect of OT rest on labor outcomes and uterine contractility compared to continuous OT during induction of labor (IOL).

Study Design: A secondary analysis of a prospective cohort study of singleton, term pregnancies admitted in labor or for IOL from January 2020 to July 2022 was performed. Inclusion criteria were nulliparity, IOL, and OT use. All patients had an intrauterine pressure catheter placed within 30 minutes of membrane rupture, regardless of labor progress. OT rest was compared to continuous OT. Primary outcomes were completion of first stage, length of active phase, and length of second stage. We used multivariable logistic regression to adjust for potential confounders. Secondary outcomes were Cesarean delivery and Montevideo units (MVUs) at three time points: active labor (cervix ≥ 6cm), max OT dose, and first stage completion. Subgroup analysis was performed to exclude OT rest for non-reassuring fetal status (NRFS).

Results: Of the 120 patients included, 55 (45.8%) had OT rest and 65 (54.1%) had continuous OT. Indications for OT rest were NRFS (73.7%), protracted labor (12.3%), and other (14.0%). Those with OT rest had significantly lower risk of completing the first stage (aRR 0.81, 95% CI 0.52-0.97). This association persisted when OT rest for NRFS was excluded (aRR 0.52, 95% CI 0.15-0.90). There were no differences in max OT dose (19.1 vs 16.7, p=0.24), length of active phase, or length of second stage (Table 1). Those with OT rest were more likely to deliver via Cesarean (Table 2). MVUs did not differ between groups at any time (Table 2).

Conclusion: Nulliparous p</span>atients who had OT rest for protracted labor were 48% less likely to complete the first stage of labor compared to those who had continuous OT; a higher proportion also delivered via Cesarean. Further research is needed to determine the utility of OT rest after diagnosis of protracted labor.