The Society for Pediatric Pathology Task Force grading system for placenta accreta spectrum and its correlation with clinical outcomes

Background: The terminology and diagnostic criteria presently used by pathologists to report placenta accreta spectrum is inconsistent and does not reflect current knowledge of the pathogenesis of this disease. Objective: In 2020, the perinatal subcommittee of the Society for Pediatric Pathology Placenta Accreta Task Force proposed a new pathologic grading system for placenta accreta spectrum. We sought to correlate the clinical outcomes with the classification into each group in the new placenta accreta spectrum grading system. Study Design: The pathology reports of patients with histopathologic confirmation of placenta accreta spectrum were reviewed in 2 academic referral centers by placental pathologists. Pathologic grading was assigned based on the new grading system according to which placenta accreta spectrum is categorized into 5 groups depending on the depth of invasion, from grade p1 with no invasion into the uterine wall to grade p3E with invasion beyond the uterine wall to the adjacent organs. Patient characteristics and clinical outcomes were compared among these groups. A univariate analysis was performed, and a multivariate linear or binomial regression was employed when needed. Results: A total of 683 patients with placenta accreta spectrum were identified. Of those, 407 were included for histology review. There were 92 patients (23%) categorized into the grade p1 group, 74 (18%) in the grade p2 group, 84 (20%) in the grade p3A group, 121 (30%) in the grade p3D group, and 36 (9%) in the grade p3E group. There was a significant association between the pathology grading and the number of red blood cells transfused (β=1.14; 95% confidence interval, 0.48–1.79) and the postoperative complications including the rate of readmission (risk ratio, 1.93; 95% confidence interval, 1.26–2.94) and bladder injury (risk ratio, 1.81; 95% confidence interval, 1.23–2.68) after adjustment for antenatal diagnosis and other variables. The pathology grading was not associated with the estimated blood loss (P=.072). Conclusion: The new pathology grading system accurately reflects maternal outcomes and complications of placenta accreta spectrum. We encourage the utilization of this new pathologic grading system because it is designed to omit discrepancies in placenta accreta spectrum reporting and to standardize communication.