INTRODUCTION:
In the absence of placenta previa, the risk of accreta is well documented (0: 0.03%, 1: 0.2%, 2: 0.1%, 3-4: 0.8%, >5: 4.7%) in the work of Silver et al. These frequently referenced risk metrics were derived from a cohort of patients delivered from 1999-2002 with a documented prevalence of accreta occurring in 1 in 2,625 deliveries. With the prevalence of accreta now approaching 1 in 533 deliveries, reevaluation of this risk is warranted.
METHODS:
A review of accreta cases presenting to a single, large, tertiary care center from 12/15/2011 to 08/22/2017 was performed. Records were reviewed and abstraction of data pertaining to demographics, obstetric history, placental location, delivery information, and tissue pathology was performed. For historical comparison, data from Silver et al was configured to reflect the risk of accreta in the absence of previa, stratified by number of prior cesareans. Data was summarized using SAS software, version 9.4.
RESULTS:
Of 169 AIP cases identified, there were 16 (9.5%) patients with prior cesarean delivery, anterior placentation, and no previa that had histologically-confirmed AIP. The risk of AIP after 1, 2, 3-4 and >5 prior cesarean deliveries was 50%, 75%, 77.8%, and 50%, respectively. No differences were observed comparing this risk to that of Silver et al (53.1%, 19.4%, 35.1%, 66.7%; p - 0.470).
CONCLUSION:
Our data suggests that absence of placenta previa should not be heavily relied upon for risk reduction when antenatal suspicion for AIP is raised based on other clinical variables.