Risk factors for nonreassuring fetal heart rate tracings after artificial rupture of membranes in spontaneous labor.

BACKGROUND: We aimed to characterize factors associated with nonreassuring fetal heart (FHR) tracings after artificial rupture of membranes (AROM), during the active phase of labor.

METHODS: Delivery charts of patients who presented in spontaneous labor, at term, between 2015 and 2016 were reviewed. We identified cases in which AROM was performed during the active stage of labor. We compared deliveries with a normal FHR and those who developed nonreassuring FHR. Nonreassuring FHR was defined as fetal tracing that necessitated intrauterine resuscitation, which included: oxytocin withheld, amnioinfusion, or immediate instrumental or cesarean birth.

RESULTS: Of 664 deliveries, nonreassuring FHR occurred in 141 (21.2%) and normal FHR in 523 (78.7%). Both groups were notable for similar maternal characteristics and a similar gestational age. Epidural block was significantly more common in the nonreassuring FHR group (P < .001), as was meconium during delivery (P = .01). Deliveries in the nonreassuring FHR group were characterized by significantly lower Bishop scores at AROM. Mean birthweight was significantly lower in the nonreassuring FHR group (3201 ± 418 vs 3342 ± 376 g, P < .001), yet, neonatal outcome did not differ between the groups. In a multivariate logistic regression model, nulliparity, AROM at a station lower than -2, and increased birthweight were all significantly associated with a decreased rate of nonreassuring FHR, while prolonged duration from AROM to delivery and oxytocin augmentation significantly increased the risk for nonreassuring FHR.

DISCUSSION: Nonreassuring FHR after AROM during delivery is associated with parity, fetal station at AROM, birthweight, and oxytocin augmentation.