Latent phase duration and associated outcomes: a contemporary, population-based observational study

Area of Science:

• Obstetrics and Gynecology
• Maternal-Fetal Medicine
• Perinatal Epidemiology

Background:

• The latent phase of labor, preceding cervical dilation to 5 cm, is poorly understood regarding its duration's impact on labor and birth.
• Investigating the latent phase is crucial for understanding labor progression and potential complications.

Purpose of the Study:

• To describe the duration of the latent phase of labor in a large Swedish population.
• To evaluate the association between latent phase duration and labor processes, birth outcomes, and neonatal outcomes, stratified by parity.

Main Methods:

• Population-based cohort study of 67,267 deliveries in Sweden (2008-2020).
• Included term, singleton, vertex, live fetuses without major malformations in spontaneous labor.
• Multivariable logistic regression analyzed associations, controlling for covariates.

Main Results:

• Median latent phase duration was 16.0 hours for nulliparous and 9.4 hours for multiparous women.
• Longer latent phase correlated with higher odds of dystocia, interventions (amniotomy, oxytocin, epidural, cesarean), fetal occiput posterior, and neonatal intensive care unit admission.
• In nulliparous women, prolonged latent phase (≥90th percentile) increased risks for adverse neonatal outcomes and chorioamnionitis.

Conclusions:

• Latent labor duration differs significantly between nulliparous and multiparous women.
• Prolonged latent phase is associated with increased dystocia, interventions, and neonatal morbidity.
• Further research is needed to elucidate pathways linking latent phase duration to neonatal outcomes.