Bleeding complications in pregnancies with low-lying placenta

To evaluate pregnancy outcomes with low-lying placenta according to the distance from placenta to cervical os.

Retrospective cohort study of singleton pregnancies with low-lying placenta (placenta edge within 20 mm of internal os on transvaginal sonography) delivered at our hospital from 2002 to 2012, excluding suspected placenta accreta and vasa previa. Vaginal delivery was offered in the absence of another indication for cesarean. Outcomes were stratified according to placenta-os distance ≤10 mm and 11-20 mm.

Of 98 pregnancies with low-lying placenta, 41% had placenta-os distance ≤10 mm and 59% placenta-os distance 11-20 mm. Fifty-four percent had a trial of labor. Six (15%) with placenta-os ≤10 mm and 21 (36%) with placenta-os 11-20 mm delivered vaginally, p = 0.02. Bleeding necessitating cesarean occurred in 25%, and postpartum hemorrhage in 43%; neither complication associated with placenta-os distance. Third-trimester bleeding prior to delivery hospitalization was reported in 44% and associated with later bleeding requiring cesarean in 51% versus 4% of those without third-trimester bleeding, p < 0.001.

Whereas low-lying placenta does not contraindicate labor, we found significant risk for bleeding complications, regardless of the planned mode of delivery. Placenta-os distance did not significantly affect outcomes in our series.