Chronic villitis: Refining the risk ratio of recurrence using a large placental pathology sample

Introduction: Chronic villitis is an inflammatory lesion that affects 5–15% of placentas and is associated with adverse pregnancy outcomes. Chronic villitis may also recur; however, studies estimating recurrence are based on small samples and estimates of recurrence range from 10 to 56%. Methods: We utilized data from placentas submitted to pathology at a Chicago hospital between January 2009 and March 2018. During the study period, 883 patients had two placentas submitted to pathology. We estimated the risk of recurrent chronic villitis, adjusted for maternal and pregnancy characteristics. We also evaluated whether prevalence of small for gestational age infant differed for those with recurrent chronic villitis and we investigated whether placental pathology worsened in the second study pregnancy among those with recurrent chronic villitis. Results: The overall prevalence of recurrent chronic villitis in the study sample was 11.5%. Among those with chronic villitis in the first pregnancy, 54% developed chronic villitis in the second pregnancy, corresponding to an adjusted risk ratio of 2.36 (95% confidence interval: 1.92, 2.91). Recurrent chronic villitis was not associated with increased prevalence of small for gestational infant as compared with non-recurrent villitis. Among those with recurrent chronic villitis, high-grade chronic inflammation and fetal vascular malperfusion were more common in the second pregnancy as compared with the first. Discussion: Our results suggest that those with chronic villitis in the first pregnancy are over twice as likely to develop chronic villitis in the second pregnancy and that chronic inflammation and fetal vascular malperfusion may worsen among those with recurrent chronic villitis.