337 High grade chronic placental inflammation is independently associated with increased risk of recurrent preterm birth

Abstract

Histologic examination of the placenta is often performed following delivery. Although placental examination cannot change the index pregnancy outcome, it may inform risk assessment for subsequent pregnancy. Prior research has examined the association between individual histologic lesions and pregnancy outcomes. The purpose of this study is to determine the association of combinations of histologic findings and risk of subsequent preterm birth (PTB). This was a retrospective cohort study of deliveries at a tertiary care center from January 2009 to March 2018. Individuals with two births and an index placental pathology report during the study period were included. The presence of maternal vascular malperfusion (MVM), fetal vascular malperfusion (FVM), maternal and/or fetal acute inflammation (AI) and chronic inflammation (CI) was extracted from the pathology report for each index placenta, classified as none, low, or high grade. A logistic model incorporating all four placental components was used to estimate associations between each histologic lesion category and risk of subsequent preterm birth, while controlling for the other lesion categories. Analysis was repeated restricting the sample only to those with an index PTB. 3926 women were included. Among all index pregnancies, presence of high grade CI and low grade MVM were associated with increased odds of subsequent PTB. AI (both low- and high-grade) and low grade FVM were associated with lower odds of subsequent PTB (Table). Among 924 index pregnancies delivering preterm, only high grade CI was independently associated with recurrent PTB (OR 1.57, 95% CI 1.02- 2.41, Figure). High-grade chronic placental inflammation in an index pregnancy is the only pathology independently associated with an increased risk of subsequent PTB, regardless of whether the index delivery is preterm or term. Decreased odds of PTB with AI and FVM in the full sample were not replicated when evaluating recurrent PTB.View Large Image Figure ViewerDownload Hi-res image Download (PPT)