Factors associated with severe postpartum hemorrhage in women with posterior low‐lying placenta and prior cesarean: A prospective population‐based study

OBJECTIVE: Our objective was to conduct an exploratory assessment of the incidence and factors associated with severe postpartum hemorrhage (PPH) in women with posterior low-lying placenta and prior cesarean without prenatal suspicion of placenta accreta spectrum (PAS). METHODS: The study population was derived from the PACCRETA population-based study conducted in the 176 maternity units of 12 French regions from November 2013 through October 2015. All women with posterior low-lying placenta and prior Cesarean without prenatal suspicion of PAS were included in this analysis. The main outcome measure was a composite criterion of severe PPH defined by either estimated blood loss of ≥1500 mL, transfusion of 4 or more units of packed red blood cells, embolization, or surgical treatment. RESULTS: Of the 520 114 women in the source population, 75 met the inclusion criteria (0.14 per 1000 women; 95% confidence interval [CI] 0.11-0.18). Among these women, severe PPH occurred in seven (i.e., severe PPH incidence of 9.3% [95% CI 4.2-18.9]). Unsuspected PAS was diagnosed at delivery in four women of the study population (5.3%). Without these cases of PAS, the severe PPH incidence was 7.0% (95% CI 2.6-16.3). Factors associated with severe PPH were unsuspected PAS diagnosed at delivery (severe PPH incidence of 50% vs. 7%, P = 0.04) and placenta-os distance 1-9 mm compared with 10-19 mm (severe PPH incidence of 19% vs. 0%, P = 0.03). CONCLUSION: About 1 in 11 women with posterior low-lying and prior cesarean without antenatal suspicion of PAS has severe PPH. Factors associated with severe PPH are unsuspected PAS diagnosed at delivery and 1-9 mm versus 10-19 mm placenta-os distance. These associations should be considered exploratory and require confirmation in larger studies.