Villitis of unknown etiology (VUE): effect on placental size and association with clinical parameters

Villitis of unknown etiology (VUE) is an inflammatory placental lesion with immune-mediated pathogenesis, diagnosed by histopathological examination. It is one of the three placental lesions which tend to recur in subsequent pregnancies, the other two being chronic histiocytic intervillositis and massive fibrin deposition. The frequency of VUE and its association with maternal, obstetric and neonatal complications are variability reported in the literature. The aim of this study is to determine the frequency of VUE in the population studied and to observe the association of specific subtypes of villitis with clinical features, placental morphometric and microscopic parameters.

Placentas where villitis was observed, were obtained from the pathology database from January 2013 to June 2018. VUE was graded as low grade (LG), high grade (HG) and basal villitis (BV) and subcategorized based on extent and cell type. Its association with selected maternal, neonatal and placental parameters was evaluated.

A total of 1603 placentas were received and 163 singleton placentas with villitis (10%) were reported. LG and HG villitis was observed in 58% and 25% cases respectively. Basal villitis was seen in 24% and pure basal villitis without involvement of parenchymal villi was seen in 16.6%. While there was near equal distribution of focal (n = 45) and multifocal (n = 50) LG villitis, diffuse HG villitis (n = 32) was more common than patchy HG villitis (n = 9). Overall villitis was more common in preterm pregnancies (59.5%) with most of them being basal villitis and low-grade villitis (64.2%, p value .029). None of the other maternal and neonatal parameters had any significance. Placental dimensions (length and breadth) showed a significant negative association with VUE, especially high-grade and multifocal low-grade villitis.

VUE was a common finding in preterm births and its novel association with placental size opens avenues for further research on alternative mechanisms involved in the association between villitis, placental function and adverse pregnancy outcomes.