Objectives: Ultrasound detection of placenta accreta spectrum (PAS) among women at risk is a key goal to reduce obstetric morbidity, but there is scarce information of its performance in real clinical settings. We report the effectiveness of a standardized ultrasound protocol to detect PAS in women with placenta previa in a secondary-level hospital.
Methods: A retrospective analysis, including a cohort of 126 women with persistent placenta previa among 27,975 pregnancies between 2008 and 2020. All 126 women underwent standardized transabdominal and transvaginal ultrasound assessing 5 criteria: 1) loss of hypoechoic retroplacental zone and/or myometrial thinning <1 mm; 2) lacunar images with flow >15 cm/sec; 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 caesarean section and by histopathological analysis.
Results: Among 126 women with placenta previa, 11 (8.7%) cases of PAS were diagnosed, of which 10 were detected prenatally by ultrasound. This resulted in a sensitivity of 90,9%, a specificity of 98,3%, a positive predictive value (PPV) of 83,3%, and negative predictive value (NPV) of 99,1%. Histopathological assessment showed six placenta increta (54.5%), four percreta (36.4%) and one accreta (9.1%). All 10 cases of invasive placenta presented more than three ultrasound criteria.
Conclusions: Standardized ultrasound screening protocol in women at risk due to placenta previa in the third trimester was highly effective in detecting PAS in a secondary-level hospital setting.