(223) How long is too long? Assessing risks of prolonged latent phase of labor

Thursday, February 9, 2023

10:30 AM – 12:00 PM

Objective: ACOG has clear guidelines on expected durations of the active phase and second stage of labor. However, there is a paucity of data on the expected length and risks of abnormal latent phase of labor. We sought to define prolonged latent phase (PLP) and examine associated morbidity.

Study Design: This is a secondary analysis of a prospective cohort study of term singleton gestations admitted for induction of labor (IOL) or spontaneous labor 2010- 2015. We included all gravidas who reached active labor. Primary outcomes were composite maternal morbidity (fever, postpartum hemorrhage, transfusion, endometritis, and higher order perineal lacerations) and composite neonatal morbidity (respiratory distress syndrome, mechanical ventilation, birth injury, seizures, hypoxic ischemic encephalopathy, therapeutic hypothermia, or umbilical artery pH < 7.1). Outcomes were compared between patients with and without PLP, defined as >90^th%ile of the duration between admission and active phase. Results were stratified by type of labor. Multivariable logistic regression was used to adjust for confounders. Receiver operating characteristic curves were used to determine predictive ability of latent phase duration for composite morbidity.

Results: In this cohort of 6509 patients, 51% underwent IOL. PLP was > 18.75 hours in the IOL group and > 8.5 hours in the labor group. Among patients with PLP, there was a significant increase in composite maternal morbidity in both IOL (aOR 1.37, 95% CI 1.01, 1.85) and spontaneous labor (aOR 1.70, 95% CI 1.26, 2.29) cohorts but no difference in composite neonatal morbidity compared to those without PLP (Table). Maternal morbidity was driven by increased risk of fever and transfusion. Latent phase duration was a modest predictor of maternal morbidity (AUC 0.69 spontaneous labor, 0.66 IOL) but a poor predictor of neonatal morbidity (Figure). Rate of cesarean delivery was 32% with PLP and 13% without PLP.

Conclusion: PLP, in both IOL and spontaneous labor, is associated with maternal morbidity but not neonatal morbidity. These data may guide considerations for latent phase management.

Primary & Presenting Author(s)

Julia Burd, MD
Fellow
Washington University School of Medicine
Saint Louis, Missouri, United States

Coauthor(s)

CW
Candice Woolfolk, MPH, PhD
Research Statistician
Washington University in St.Louis
St. Louis, Missouri, United States
MD
Michael Dombrowski, MD
Washington University in St.Louis
St. Louis, Missouri, United States
Ebony B. Carter, MD, MPH (she/her/hers)
Associate Professor, MFM; Chief, Division of Clinical Resarch
Washington University School of Medicine
St. Louis, Missouri, United States
JK
Jeannie C. Kelly, MD,FACOG,MS
Associate Professor
Washington University School of Medicine
St. Louis, Missouri, United States
Antonina I. Frolova, MD,PhD (she/her/hers)
Assistant Professor
Washington University School of Medicine
St. Louis, Missouri, United States
Anthony O. Odibo, MD
Professor
Washington University School of Medicine
St. Louis, Missouri, United States
Alison G. Cahill, MD, MSCI
Professor
University of Texas at Austin, Dell Medical School
Austin, Texas, United States
Nandini Raghuraman, MD,MSc (she/her/hers)
Assistant Professor
Barnes Jewish Hospital, Washington University in St Louis
St. Louis, Missouri, United States