1135 Sensitivity of antenatal ultrasound in diagnosing posterior placenta accreta spectrum disorders

Abstract

Placenta accreta spectrum (PAS) is associated with increased morbidity and mortality, particularly in the absence of optimal preoperative preparation. Limitations of ultrasound (US) may decrease the detection of posterior PAS. We sought to evaluate the typical US findings of PAS as they apply to detection of posterior PAS. Cohort study of patients with a posterior placenta and pathology-confirmed PAS from 2011-2020 at a tertiary care center. Cases were identified using a natural language search engine with key terms “accreta/increta/percreta” and “posterior.” Patients were excluded if US images were unavailable or if there was a complete previa with <50% extension posteriorly. US images were reviewed by accredited MFM specialists for the presence of lacunae, hypervascularity, and myometrial thinning <2mm. Risk factors, postpartum outcomes, and US findings were compared and stratified by antepartum suspicion for PAS. χ2 and t-test was used. Sensitivity was calculated for each US finding. The search yielded 706 charts; 47 patients had pathology-confirmed posterior PAS, of which 33 had US images available for review. PAS was not suspected antenatally in 70% (n=23). Patients with unsuspected PAS were more likely be non-Hispanic, have in-vitro fertilization, no prior Cesarean deliveries, no previa, and delivered later in gestation (Table 1). Depth of invasion and estimated blood loss were less for unsuspected PAS, but there was no difference in hysterectomy between groups. US findings were less frequently seen in those who were not suspected antenatally: lacunae 17.4% vs 100% (p<0.01), hypervascularity 8.7% vs 80% (p<0.01), and myometrial thinning 4.4% vs 70% (p<0.01). There was poor sensitivity (24.2-42.4%) for all findings (Table 2). Our data suggests that posterior PAS is less likely to be detected antenatally due to a lower sensitivity of typical US findings of PAS in the setting of a posterior placenta. Further studies are needed to better identify reliable markers of posterior PAS to allow for appropriate preoperative preparation and to mitigate maternal risk.View Large Image Figure ViewerDownload Hi-res image Download (PPT)