Accuracy of Placenta Accreta Index in Diagnosing Placenta Accreta Spectrum

The placenta accreta spectrum (PAS) which includes accreta, increta, and percreta represents a significant obstetric challenge. PAS complicates as many as 1 per 500 pregnancies and this risk is increased with prior cesarean deliveries. Antenatal diagnosis of PAS allows for multidisciplinary planning and delivery before the onset of labor and/or vaginal bleeding. This approach has reduced maternal morbidity rates, including less blood loss, fewer transfusion requirements and, intraoperative urologic injuries as well as improve fetal outcome.

Ultrasound evaluation, with grayscale and color Doppler imaging, is the recommended first-line modality for diagnosing PAS. Grayscale ultrasound features suggestive of placenta accreta include an inability to visualize the normal retroplacental clear zone, irregularity, and attenuation of the uterine-bladder interface, retroplacental myometrial thickness, presence of intraplacental lacunar spaces, and bridging vessels between the placenta and bladder wall when using color Doppler.

The placenta accreta index (PAI) score (a nine-point score) was proposed in 2015 to predict PAS based on US parameters in a high-risk population by retrospective data analysis. The probability of histological invasion was found to increase with increasing the PAI score. This study aimed to prospectively evaluate the diagnostic performance of the PAI in the prediction of PAS in relation to histopathological findings.