Effectiveness of Ultrasound Screening for a Placenta Accreta Spectrum Using Standard Ultrasound Criteria in a Secondary Care Setting

Abstract

Objectives: Ultrasound detection of a placenta accreta spectrum (PAS) among women at risk is a key goal to reduce obstetric morbidity, but there is scarce information on its performance in real clinical settings. We report the effectiveness of a standardized ultrasound protocol to detect PAS in women with placenta previa (PP) in a secondary-level hospital.

Methods: A retrospective analysis, including a cohort of 126 women with persistent PP among 27,975 pregnancies between 2008 and 2020, was performed. All 126 women underwent standardized transabdominal and transvaginal ultrasound scan that assessed 5 criteria: (1) loss of hypoechoic retroplacental zone and/or myometrial thinning <1 mm; (2) lacunar images with a flow of >15 cm/s; (3) thick and bulging placenta; (4) thinning or interruption of the uterine-bladder serous interface; and (5) placental or uterovesical hypervascularity. The presence of at least one criterion was considered a high risk for PAS. Diagnosis of PAS was confirmed during the caesarean section and by histopathological analysis.

Results: Among 126 women with PP, 11 (8.7%) cases of PAS were diagnosed, of which 10 were detected prenatally by ultrasound scan. This resulted in a sensitivity of 90.9%, a specificity of 98.3%, a positive predictive value of 83.3%, and a negative predictive value of 99.1%. Histopathological assessment showed 6 placenta increta (54.5%), 4 percreta (36.4%), and 1 accreta (9.1%). All 10 cases of invasive placenta presented more than 3 ultrasound criteria.

Conclusions: Standardized ultrasound screening protocol in women at risk due to PP in the third trimester was highly effective in detecting PAS in a secondary-level hospital setting.

Keywords: Caesarean section; Placenta accreta spectrum; Placenta previa; Ultrasound screening.