Antenatal diagnosis and classification for placenta accreta (adherence) spectrum: Clinical practice guideline and recommendations by the World Association of Perinatal Medicine and the Perinatal Medicine Foundation

Abstract

This practical guidance was developed by the World Association of Perinatal Medicine in collaboration with the Perinatal Medicine Foundation to support antenatal diagnosis and clinical management in pregnancies at risk for placenta accreta spectrum (PAS). It provides an evidence‐informed approach to screening, diagnosis, referral, and peripartum planning across healthcare settings with different resources. PAS is increasingly encountered alongside rising cesarean delivery rates, use of in vitro fertilization, and a history of uterine surgery. It remains associated with severe maternal morbidity, including massive hemorrhage, large‐volume transfusion, uterine rupture, peripartum hysterectomy, pelvic organ injury, intensive care admission, and maternal death. Early recognition and multidisciplinary care are therefore central to management. Cesarean scar pregnancy (CSP) is considered a potential precursor of PAS. Women with a low implantation site and a previous cesarean delivery are at increased risk. Early transvaginal ultrasound is advised in women with a previous cesarean delivery to establish the implantation site, identify CSP, and support counseling and timely consideration of uterine‐preserving treatment. In the second and third trimesters, combined transabdominal and transvaginal ultrasound assesses placental location, myometrial thickness and contour, and the uterovesical interface. Sonographic markers include placental lacunae, placental bulge, uterovesical hypervascularity, and bridging vessels, which may occur individually or in combination. Two‐dimensional grayscale ultrasound is the mainstay of antenatal assessment, supported by color Doppler; three‐dimensional imaging may provide additional information in selected specialist settings. Magnetic resonance imaging has a complementary role when ultrasound is inconclusive, placental location is non‐anterior or non‐previa, or technical factors limit visualization. Suspected CSP or PAS should prompt referral to a perinatal center with multidisciplinary expertise, blood product support, adult and neonatal intensive care, and access to complex pelvic surgery. Delivery timing and surgical preparation should be individualized.