Assessment of prevalence and seasonal variation of chronic villitis of unknown aetiology: An Australian study.

Abstract

Background: The incidence of villitis of unknown aetiology (VUE) in most studies is between 5-15%. There are some recent data in the literature postulating a possible seasonal trend in incidence of VUE, with one study showing higher risk of VUE during the fall and winter. This revelation may potentially bring insight into the underlying pathogenesis of VUE and elucidate possible contribution of undiagnosed infection(s) in development of this condition. Aim(s): The aim of this study is to investigate the prevalence of VUE and its seasonal trend in placentas examined in an Australian tertiary hospital over a 26-month period. Method(s): A total of 436 placentas were evaluated; they were all submitted for routine examination to Histopathology Department at Monash Medical Centre, VIC from January 2019 to February 2021, and reported by one perinatal pathologist (AM). Data included in the histology reports were retrospectively collected and used for the analysis. Result(s): In 53 placentas (12.15%), a diagnosis of VUE was rendered. The majority of VUE (77.35%) were low-grade. The peak incidence of VUE was in the placentas delivered in April (25%) followed by those delivered in December (21.05%), January (19.4%) and May (15.15%). The highest combined prevalence of VUE were among those placentas delivered in March-May quarter of the year (19.9%) and December-February quarter (14.28%). In total, 66% of the placentas with VUE were delivered between December and May. Conclusion(s): The overall prevalence of VUE in our cases is aligned with the reports from previous studies. The results from our cohort also reveal a seasonal trend to the prevalence of VUE: Higher relative frequencies of VUE are observed during the summer and autumn seasons (of the Southern Hemisphere). Further research from different geographical locations would be necessary to gather information in order to test this hypothesis and investigate the underlying cause for this pattern of presentation.