Placenta Accreta Spectrum: Prediction with Ultrasound Markers

Abstract

Introduction: Placenta accreta spectrum (PAS) causes life-threatening postpartum hemorrhage. Prenatal diagnosis reduces morbidity. Optimal ultrasound markers for prediction in at-risk patients (previous cesarean + placenta previa) need standardization. Methods: Systematic review of 18 cohort studies (n=1,203) evaluating ultrasound markers for PAS. Markers: loss of retroplacental clear zone, myometrial thinning (<1 mm), lacunae (grade 2-3), bridging vessels, bladder wall interruption. Reference standard: intraoperative/histologic confirmation. Results: Loss of clear zone had 87% sensitivity (95% CI 81-92%) but 59% specificity. Myometrial thinning <1 mm had 89% sensitivity and 78% specificity. Multiple lacunae had 94% specificity (91-97%) but only 55% sensitivity. Combining ≥3 markers gave sensitivity 96% and specificity 88% (AUC 0.92). Discussion: No single marker is sufficient. Combination scores require validation. Interobserver agreement for lacunae grading is moderate (kappa 0.56). Conclusion: A combination of three or more ultrasound markers accurately predicts PAS in high-risk patients, allowing planned delivery at specialized centers.