The association between longer durations of the active phase of labor and subsequent perinatal processes and outcomes among midwifery patients

Background/Objective
To evaluate the association between the duration of the latent phase of labor and subsequent processes and outcomes.

Methods
Secondary analysis of prospectively collected data among 1,189 women with low-risk pregnancies and spontaneous labor.

Results
Longer latent phase duration was associated with labor dystocia (eg, nulliparous ≥ mean [compared with < mean] aOR 3.95 [2.70-5.79]; multiparous ≥ mean [compared with < mean] aOR 5.45 [3.43-8.65]), interventions to ameliorate dystocia, and epidurals to cope or rest (eg, oxytocin augmentation: nulliparous > 80th% [compared with < 80th%] aOR 6.39 [4.04-10.12]; multiparous ≥ 80th% [compared with < 80th%] aOR 6.35 [3.79-10.64]). Longer latent phase duration was also associated with longer active phase and second stage. There were no associations between latent phase duration and risk for cesarean delivery or postpartum hemorrhage in a practice setting with relatively low rates of primary cesarean. Newborns born to multiparous women with latent phase of labor durations at and beyond the 80th% were more frequently admitted to the NICU (≥80th% [compared with < 80th%] aOR 2.7 [1.22-5.84]); however, two-thirds of these NICU admissions were likely for observation only.

Conclusions
Longer duration of the spontaneous latent phase of labor among women with low-risk pregnancies may signal longer total labor processes, leading to an increase in diagnosis of dystocia, interventions to manage dystocia, and epidural use. Apart from multiparous neonatal NICU admission, no other maternal or child morbidity outcomes were elevated with longer duration of the latent phase of labor.