Incidence and risk factors for severe postpartum haemorrhage in women with anterior low-lying or praevia placenta and prior caesarean: Prospective population-based study.

OBJECTIVE

To assess the incidence and risk factors for severe postpartum haemorrhage (PPH) in women with an anterior low-lying or praevia placenta, prior caesarean and no prenatal suspicion of placenta accreta spectrum (PAS).

DESIGN

Population-based study in 176 maternity units in France.

POPULATION: All women with anterior low-lying (0-19 mm from the cervical internal os) or praevia placenta, diagnosed prospectively before birth, prior caesarean and no prenatal suspicion of PAS.

METHODS

Multivariable logistic regression to identify risk factors for severe PPH in the main population and after exclusion of women with PAS diagnosed only at birth.

MAIN OUTCOME MEASURES: Severe PPH defined by a composite criterion either estimated blood loss of ≥1500 ml, transfusion of ≥4 or more units of packed red blood cells, embolisation or surgical treatment.

RESULTS

Of the 520 114 women constituting the source population, 230 (0.44/1000 women; 95% confidence interval [CI] 0.38-0.50) met the inclusion criteria. Severe PPH rate was 24.8% (95% CI 19.2-30.4) overall, 27.5% (95% CI 21.8-33.3) in women with placenta praevia and 15.4% (95% CI 10.7-20.0) in women with low-lying placenta. PAS was diagnosed at birth in 22 women (9.9%; 95% CI 5.8-13.4), although previously unsuspected. After their exclusion, severe PPH incidence was 17.3% (95% CI 12.4-22.2). In multivariate analysis, the only factor associated with a higher severe PPH risk was placenta previa (aOR, 3.65; 95%CI, 1.20-15.8).

CONCLUSION

Severe PPH is frequent among women with anterior low-lying or praevia placenta and prior caesarean, even after exclusion of women with PAS. The risk of severe PPH for those with praevia is nearly twice that with low-lying placenta.