Assessment of ultrasound features of placenta accreta spectrum in women at high risk: association with outcome and interobserver concordance.

Objectives: To evaluate the prenatal ultrasound features associated with operative complications and to assess the interobserver agreement of prenatal ultrasound assessment with histopathologic confirmation of placenta accreta spectrum (PAS) in a cohort of high-risk patients with detailed intraoperative and histopathologic data.

Methods: This was a retrospective multicenter cohort study of patients at high risk of PAS referred for specialist perinatal care and management between January 2019 and May 2022. Deidentified ultrasound images were reviewed independently by two experienced operators blinded to clinical details, intraoperative features, outcome and histopathologic findings. The diagnosis of PAS was confirmed by failure of detachment of one or more placental cotyledons from the uterine wall at delivery, and the absence of decidua with distortion of the uteroplacental interface by fibrinoid deposition on histologic examination of the accretic areas obtained by guided sampling of partial myometrial resection or hysterectomy specimens. Patients were categorized as having a low or high likelihood of PAS at birth. Interobserver agreement of prenatal ultrasound assessment with histopathologic confirmation of PAS was assessed using the kappa statistic. Primary outcome was major operative morbidity (blood loss ≥ 2000 mL, unintentional injury to the viscera, admission to intensive care unit or death).

Results: A total of 102 women at high risk of PAS were referred, of whom 66 had evidence of PAS at birth and 36 did not. When blinded to other clinical details, the examiners agreed on the low or high probability of PAS, according to ultrasound features, in 75/102 cases (73.5%). The kappa statistic was 0.47 (95% CI, 0.28-0.66), showing moderate agreement. Morbidity was twice as common with concordant prenatal diagnosis of PAS vs concordant diagnosis of not PAS. Concordant assessment of high probability of PAS was associated with the highest morbidity (66.6%) and a very high (97.6%) likelihood of histopathologic confirmation.

Conclusions: The probability of histopathologic confirmation is very high with concordant prenatal assessment suggestive of PAS. The interobserver agreement for preoperative assessment with histopathologic confirmation of PAS is only moderate. Morbidity is associated with both histopathologic diagnosis and concordant antenatal assessment of PAS. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.