Obstetrical and Neonatal Outcomes of Term Pregnancies Complicated by Unstable Fetal Lie

Unstable fetal lie, characterized by frequent changes in fetal presentation during late pregnancy, poses challenges in pregnancy management and delivery planning. We aimed to examine the obstetrical and neonatal outcomes associated with term pregnancies complicated by an unstable fetal lie.

This retrospective cohort study included data recorded during 2012-2022 of women with term singleton pregnancies with an unstable fetal lie who attempted vaginal delivery after stabilizing to vertex. We compared their obstetrical and neonatal outcomes in a 1:2 ratio to those of women without a history of unstable fetal lie who had a singleton fetus in vertex presentation at delivery.

Of 67,360 deliveries, 174 (0.25%) were with an unstable fetal lie. For women who attempted vaginal delivery (n = 116, 66.7%) compared to women with spontaneous vertex presentation who delivered vaginally (n = 232), the intrapartum cesarean delivery (CD) rate was higher (31.0% vs. 10.3%, p < 0.001). Also higher were the CD rates attributed to fetal distress (12.9% vs. 6.0%, p = 0.038) and labor dystocia (11.2% vs. 4.7%, p = 0.041), and the nuchal cord incidence rate (17.2% vs. 5.6%, p < 0.001). Multivariate logistic regression identified unstable fetal lie as an independent risk factor for emergent CD (OR 4.1, 95% CI 2.1-8.2, p < 0.001). Birth trauma, cord prolapse, and perinatal death were not reported.

Vaginal delivery attempts in women with an unstable fetal lie did not show similar progression of labor and obstetrical outcomes as spontaneous vertex presentation. This emphasizes the need for tailored management.