Incidence and Risk Factors for Placenta Accreta Spectrum in Placenta Previa: Impact of Placental Type and Location

Background: The incidence of placenta accreta spectrum (PAS) with placenta previa has been previously reported. However, the incidence varies across reports, suggesting that unknown risk factors may be involved. This study aimed to reevaluate the risk of PAS in patients with placenta previa. Methods: This multicenter retrospective study was conducted from 2015 to 2024 in patients with placenta previa who underwent cesarean section (CS). PAS was defined based on pathological or clinical findings, such as manual removal of the placenta or obvious retention of the placenta if a hysterectomy was not performed. The incidence of PAS and associated risk factors were analyzed using multivariable logistic regression. Results: PAS was observed in 26% of women with placenta previa. The incidence of PAS increased significantly with the number of prior CSs: 13.2% in women with no prior CS, 41.9% in those with one prior CS, and 66.7% in those with two or more prior cesarean sections. Multivariate analysis identified major placenta previa (aOR 2.69, 95% CI 1.11–6.54), including complete and partial placenta previa, and number of prior CSs (one prior: aOR 4.35, 95% CI 1.94-9.73; two or more prior: aOR 9.48, 95% CI 2.55-35.2) as independent risk factors. Conclusions: The incidence of PAS with placenta previa was higher than that previously reported, and major placenta previa was shown to be an independent risk factor, regardless of prior CS history. Comprehensive evaluation, including prior CS and placenta previa classification, is crucial for accurate risk stratification and perinatal management.