Abstract
The practical significance of microscopic accreta (adherent basal plate myometrial fibers) is unknown, making counseling to affected patients challenging. We hypothesized that microscopic accreta (MIP) in a prior pregnancy is a significant risk factor for placenta accreta spectrum (PAS). Retrospective cohort study of subjects who had two consecutive pregnancies delivered at our single hospital, high-volume quartiary care center over the time interval from 2012-2019. All included subjects in this analysis (n=1197) underwent detailed placental pathology with a boarded pediatric pathologist subspecializing in placental pathology, inclusive of gross exam, detailed histology, and cytology and/or vascular mapping as indicated. Patients with a pathologic diagnosis of MIP in prior pregnancy (exposed/cases; n=197) were compared with a randomly selected sample of 1000 patients without diagnosis of MIP (unexposed/controls) based on a power estimation to detect a group-wise difference of ≥2% at a a of 0.8 (80%, p 0.05). Characteristics of cases vs controls were compared in a subsequent index pregnancy using descriptive statistics. After appropriately adjusting for potential confounders, the predictive power of MIP to discriminate index PAS was evaluated using logistic regression analysis with calculation of adjusted relative risk (aRR). Comparison against well-recognized clinical risk factors was performed to aid in counseling. Level of significance was set at 0.05. Characteristics are shown in Tables. 6/197 (3%) of subjects with MIP developed PAS in their subsequent index pregnancy. This rate was significantly higher than those without MIP (10/1000, 1%; p=0.02). The crude RR of PAS among MIP was 3.10 (1.11-8.65; p=0.029) and aRR of PAS was 3.01 (1.08-7.46; p=0.031), 2.91 (1.06-6.83, p=0.040), and 2.86 (1.05-6.28, p=0.041) after adjustment for number of prior CS, IVF, and placenta previa respectively. Our data suggests that microscopic accreta is an independent risk factor for placenta accreta spectrum in subsequent pregnancy irrespective of other known risk factors.View Large Image Figure ViewerDownload Hi-res image Download (PPT)
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