Risk factors and clinical significance of placental basal plate myometrial fiber: a single center experience

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. Several areas of further investigation were also proposed such as clinical significance and risk factors of placental basal plate myofiber (BPMF), previously known as macroscopic accreta. Therefore, we sought to investigate the risk factors and maternal complications and outcomes such as risk of blood loss and need for blood product replacement if BPMF was present. We performed a retrospective cohort of all patients with placental histopathological evaluation in a tertiary hospital from august 2012 to March 2020. We compared the clinical characteristics and outcomes between the group with BPMF versus the group with no evidence of BPMF upon re-evaluation of placental pathological slides. Of all the patients with placental histopathological evaluation (n = 1679), 211 (13%) had BPMF confirmed. The group of patients with BPMF delivered later in gestation (39 weeks [IQR 38, 40] vs. 38 [IQR 36, 39], p < 0.001), had higher maternal age (31 years [IQR 29, 33] vs. 29 years [IQR 25, 33], p < 0.001), and were more likely to have a pregnancy resulted from IVF (10.9% vs. 4.4%, p < 0.001). Clinical outcomes including maternal bleeding (600 mL [IQR 310, 850] in the BPMF group vs. 600 mL [IQR 300, 800] in the non-BPMF group, p = 0.371], and occurrence of RBC transfusion (1.4% in the BPMF group vs 2.7% in the non-BPMF group, p = 0.353) were similar between study groups (Table). In vitro fertilization is an independent risk factor for BPMF. Presence of BPMF does not increase the risk of blood loss and need for blood products replacement at the time of delivery.