Interobserver agreement on standardized ultrasound and histopathologic signs for the prenatal diagnosis of placenta accreta spectrum disorders

Objective: To evaluate interobserver agreement in assessment of ultrasound signs and histopathologic findings associated with placenta accreta spectrum (PAS) disorders. Methods: A retrospective study was conducted using data for patients prenatally diagnosed with PAS disorders at a UK hospital between January 31, 2012, and March 30, 2017. Ultrasound images (including gray-scale and color Doppler imaging [CDI] parameters) and histopathologic slides were reviewed by two observers; the level of agreement was calculated. Results: Among 25 patients, 11 had placenta creta, 10 had placenta increta, and four had placenta percreta. Interobserver agreement for ultrasound imaging in the second and third trimesters and histopathologic diagnosis of PAS was rated as good-to-excellent. The highest level of interobserver agreement for ultrasound signs was found for loss of clear zone (100%) and substantial myometrial thinning (96%-100%) on gray-scale imaging, the presence of lacunar feeder vessels (100%) on two-dimensional CDI, and crossing vessels and lacunae (92%-95%) on three-dimensional CDI. Conclusion: Standardized ultrasound signs might prove useful for prenatal screening of women at risk of PAS disorders and should enable remote evaluation of images when PAS is suspected.