Recurrence risk of villitis of unknown etiology: Analysis of a large retrospective cohort study, systematic review and meta-analysis.

Abstract

Recurrence risk of villitis of unknown etiology (VUE) remains uncertain because of few studies and their methodologic limitations. We calculated recurrence risk in a large population of deliveries after minimizing important biases and compared it to others via systematic review and meta-analysis. Over 11 years of placenta pathology reports on singleton deliveries were retrieved and searched for 'villitis' or 'VUE'. Cases of acute villitis and chronic villitis from infections were eliminated via pathologist review. Reports were merged to data containing gestational age, parity and gravida. Recurrence risk of VUE per patient, per parity and per gravida was determined among patients with ≥2 placentas examined for deliveries ≥20 weeks gestation. Results were compared to those from articles and their references identified by a MEDLINE® search. Recurrence risks among methodologically similar studies were pooled using a random effects model. Among 29124 placenta pathology reports from 27087 patients, there were 2423 cases of VUE among 2382 patients, of which 153 had ≥2 placentas examined. There were 41 recurrent cases of VUE for a recurrence risk of 27% per patient, 22% per parity, and 19% per gravida. We identified 64 articles, of which 4 were retained. One examined all placentas from all births over a ∼3-year period, finding a recurrence risk of 27%. The remaining 3 studies, along with our own, used indications for placental examination and had a pooled recurrence risk of 30% (95% Confidence Interval: 0.21-0.41). In our study, which is the largest, most comprehensive, and methodologically robust to date, VUE recurrence risk was ∼30%.