Trial of Labor Compared With Elective Cesarean Delivery for Low-Lying Placenta

Objective: To compare outcomes of women with low-lying placenta by planned mode of delivery and distance from the internal os distance.

Methods: Six tertiary maternity hospitals in France participated in this retrospective multicenter study of births from 2007-2012. Women with low-lying placenta , defined as an internal os distance of 20 mm or less, who gave birth after 35 weeks of gestation were included and classified in the planned trial-of-labor or elective cesarean delivery groups. The primary endpoint was severe postpartum hemorrhage (PPH) defined as blood loss exceeding 1,000 mL. Secondary outcomes were composite variables of severe maternal and neonatal morbidity. We used multivariable logistic regression and propensity scores to compare outcomes by planned mode of delivery.

Results: Among 128,233 births during the study period, 171 (0.13%) women had low-lying placenta: 70 (40.9%) in the trial-of-labor group and 101 (59.1%) who underwent elective cesarean delivery. The rate of severe PPH was 22.9% (16/70, 95% CI 13.7-34.4) for the trial-of-labor group and 23.0% (23/101, 95% CI 15.2-32.5) for the cesarean delivery group ( P =.9); severe maternal and neonatal morbidity rates were likewise similar (2.9% vs 2.0% [ P =.7] and 12.9% vs 9.9% [ P =.5], respectively). Trial-of-labor was not significantly associated with a higher rate of severe PPH after multivariable logistic regression and propensity score-weighted analysis (adjusted odds ratio [aOR] 1.42, 95% CI 0.62-3.24 [ P =.4]; and aOR 1.34, 95% CI 0.53-3.38 [ P =.5], respectively). The vaginal delivery rate in the trial-of-labor group was 50.0% (19/38) in those with an internal os distance of 11-20 mm and 18.5% (5/27) in those with a distance of 1-10 mm.

Conclusion: Our results support a policy of offering a trial of labor to women with low-lying placenta after 35 weeks of gestation and an internal os distance of 11-20 mm. An internal os distance of 1-10 mm reduces the likelihood of vaginal birth considerably, compared with 11-20 mm, but without increasing the incidence of severe PPH or severe maternal morbidity.