Placental villitis of unknown origin: Epidemiologic associations

Objectives This study was undertaken to investigate the incidence and associations of placental villitis of unknown origin or etiology (VUE). Study design Five hundred nine placentas from women delivered of small-for-gestational-age infants (SGAP) and 529 placentas from women delivering infants with birth weights appropriate for gestational age (AGAP) were examined prospectively for VUE as part of a population-based case control study of SGA infants at term. Results VUE was found in 17.3% of SGAP and 11.7% of AGAP and was an independent risk factor for SGA (adjusted odds ratio 2.35, 95% CI 1.55-3.56). Villitis in conjunction with maternal hypertension increased the risk of SGA substantially (adjusted odds ratio 17.7, 95%CI 3.6-86.9). A study of a wide range of pregnancy-related factors found no significant associations with VUE in AGAP. In contrast, VUE in SGAP had significant associations after multivariate analysis with maternal body mass index, multigravidity, ethnicity, and 1 index of maternal infection. Conclusion VUE is an independent risk factor for SGA at term. Maternal factors influence this association, possibly by modifying a systemic effect on fetal growth of villous inflammation at commonly occurring defects in the maternal-fetal immune barrier.