Contemporary Placenta Accreta Spectrum Disorder Incidence and Risk Factors.

Objective: To establish contemporary rates of maternal morbidity and placenta accreta spectrum (PAS) based on history of cesarean delivery and placental location at a single institution.

Methods: This is a retrospective cohort study conducted between January 2011 and May 2024. All patients who delivered by cesarean were included. Maternal demographics and morbidities, including rates of PAS, placenta previa, transfusion, and hysterectomy, were compared according to the increasing number of cesarean deliveries. The effect of low-lying placenta or placenta previa and their respective locations were also analyzed. Odds ratios were calculated for risk of PAS and hysterectomy on the basis of number of cesarean deliveries and the placental location in the lower uterine segment.

Results: A total of 44,608 cesarean deliveries were performed. With increasing number of cesarean deliveries, patients were older (33.3±5.3 years), were more frequently Black, and had a lower median gestational age at the time of delivery (38 weeks, interquartile range 37-39 weeks, all P <.001). With increasing cesarean deliveries, rates of PAS (0.03% vs 0.3% vs 0.8% vs 1.7% vs 2.8%, P <.001), hysterectomy (0.5% vs 0.5% vs 1.2% vs 2.6% vs 4.2%, P <.001), and blood transfusion and total operative time increased. Rates of anterior placenta previas (0.35% vs 0.29% vs 0.49% vs 0.89% vs 1.09%, P <.001) and low-lying placentas (0.09% vs 0.06% vs 0.12% vs 0.28% vs 0.44%, P <.001) also increased. The rate of PAS in the setting of placenta previa and low-lying placenta increased with increasing cesarean deliveries, at 2.22%, 28.9%, 62.5%, 64.9%, and 43.8% ( P <.001) and 0%, 10.3%, 15.4%, 17.6%, and 33.3% ( P =.001). Odds ratios for PAS were significantly higher with increasing cesarean deliveries and anterior placenta previa or anterior low-lying placenta.

Conclusions: Morbidity increases with increasing number of successive cesarean deliveries, likely secondary to increasing rates of abnormal placentation, PAS, and worsening adhesive disease. Placental location in the context of low-lying placenta or placenta previa is important in determining PAS risk, especially in cases with an anterior component.