Placenta accreta result of postoperative surgical remodeling or a preexisting uterine pathology: AJOG

To standardize the definition of PAS categories, the International Federation of Gynecology and Obstetrics (FIGO) has recently proposed a new classification for the diagnosis and grading of PAS, which includes clinical criteria at delivery confirmed by histopathologic findings of villous adherence or invasiveness. The main objective of this study by Jauniaux E and team was to prospectively evaluate the agreement between diagnosis of FIGO grade 3 (percreta) based on intraoperative clinical assessment and final pathology report diagnosis. This cohort study and systematic review of case reports described as placenta percreta in the literature found no documentation of villous tissue invading the full thickness of the myometrium; in particular, no histologic sample or literature image showed transmural villous invasion.

Authors evaluated the agreement between the intraoperative findings using the International Federation of Gynecology and Obstetrics classification with the postoperative histopathology diagnosis in a prospective cohort of 101 consecutive singleton pregnancies presenting with a low-lying placenta or placenta previa, a history of at least 1 prior cesarean delivery and ultrasound signs suggestive of placenta accreta spectrum. Furthermore, a systematic literature review of case reports of placenta percreta, which included histopathologic findings and gross images, was performed.

Samples for histologic examination were available in 80 of 101 cases of the cohort, which were managed by hysterectomy or partial myometrial resection. Microscopic examination showed evidence of placenta accreta spectrum in 65 cases. Of 101 cases included in the cohort, 44 (43.5%) and 54 (53.5%) were graded as percreta by observer A and observer B, respectively. There was a moderate agreement between observers. Of note, 11 of 36 cases that showed no evidence of abnormal placental attachment at delivery and/or microscopic examination were classified as percreta by both observers. The systematic literature review identified 41 case reports of placenta percreta with microscopic images and presenting symptomatology, suggesting that most cases were the consequence of a uterine rupture. The microscopic descriptions were heterogeneous, and all descriptions demonstrated histology of placenta creta rather than percreta.

This cohort study and systematic review of case reports described as placenta percreta in the literature found no documentation of villous tissue invading the full thickness of the myometrium; in particular, no histologic sample or literature image showed transmural villous invasion. The main intraoperative features and histologic findings suggested that most, if not all, cases reported as placenta percreta in the literature were the consequence of a complete or partial uterine rupture, dehiscence, or adhesions mainly between the anterior lower uterine segment and posterior wall of the bladder. Furthermore, these findings suggested that in women with a history of previous CD presenting with an anterior low-lying placenta or placenta previa, which currently account for 90% of all cases of PAS reported in the literature, the macroscopic features will often lead to a false-positive diagnosis of PAS in general and placenta percreta in particular.

The results of this study have provided evidence that PAS is not an invasive disorder of placentation but primarily the consequence of postoperative surgical remodeling or a preexisting uterine pathology. These findings have challenged the existence of placenta percreta as defined by histopathology and the theory that the severity of PAS is linked to the abnormal invasiveness of the villous tissue. Histopathologic findings in PAS may not have much impact on the management of the individual patient but are essential for a better understanding of the epidemiology, pathophysiology, and management of complex CDs, whether or not associated with abnormal placental attachment

Source: Jauniaux E, Hecht JL, Elbarmelgy RA, et al. Searching for placenta percreta: a prospective cohort and systematic review of case reports. Am J Obstet Gynecol 2022;226:837.e1-13.

https://doi.org/10.1016/j.ajog.2021.12.030