Chronic Intervillositis of Unknown Etiology (CIUE): Prevalence, patterns and reproductive outcomes at a tertiary referral institution

Abstract Introduction the objective of this study was to evaluate the incidence of Chronic Intervillositis of Unknown Etiology (CIUE) at our institution and to report on the pregnancy outcomes based on severity of lesions. Methods retrospective cohort study including 29 889 perinatal specimens from 27 968 patients. The pathology database at our institution was queried for the keywords “intervillositis” and “CIUE” between February 2006 and April 2019. Histology was re-examined using a standardized diagnostic criterion to confirm diagnosis. Cases in which diagnosis was confirmed were categorized as low grade (5–49% intervillous space involvement) or high grade (≥50% involvement). Interventions and pregnancy outcomes were recorded. Results The overall prevalence of CIUE is 0.17% (47 of 27 968 patients), with significantly higher prevalence in 1st trimester products of conception compared with 2nd and 3rd trimester specimens (0.38% vs 0.09%; p  Discussion CIUE prevalence is low at 0.17%, but it is associated with pregnancy loss, particularly in the first trimester. High grade disease may be associated with worse pregnancy outcomes than low grade disease.