OC08.02: Outcomes of Pregnancies at High Risk for Placenta Accreta Spectrum Following Negative Diagnostic Imaging

To assess the consequences of missed diagnoses of placenta accreta spectrum (PAS) in a high-risk population as well as the resources required to manage them. We studied a retrospective cohort with clinical risk factors for suspected PAS that delivered at our hospital between January 1, 2013 and December 31, 2019. Risk factors included: history of Caesarean delivery and placenta previa; >3 uterine surgeries, Caesarean scar pregnancy; and history of PAS. All patients had US performed by maternal fetal medicine specialists and selected patients were referred for MRI. Imaging was considered positive if either US or MRI suggested PAS. Histopathology was the gold standard for PAS. During the study period, we managed 53 patients suspected of PAS based on antenatally identified clinical risk factors. Of these, 41 (77%) had proven PAS. Imaging correctly identified 85% (35/41) of the PAS cases. Of 12 patients with negative imaging, 6 (50%) had PAS. Of these, four had either surgical complications or required care beyond that for routine Caesarean section. Although diagnostic imaging is sensitive, post-imaging PAS probability remains high in patients with high preimaging probability. Therefore high-risk patients should be managed in experienced centres by a multidisciplinary team even if imaging did not suggest PAS.