Objective: The purpose of this study was to determine, in a large preterm cohort (20-34 completed weeks of gestation), the incidence of histologic chorioamnionitis and the incidence of a histologic fetal response to chorioamnionitis (umbilical vasculitis with or without funisitis) in neonatal survivors (to 28 days) and perinatal deaths.
Study design: Placental histopathology was reviewed (n=3928 reports). In a subset of this cohort (n=2076 reports), evidence of a histologic fetal response was compared in neonatal survivors and perinatal deaths.
Results: The incidence of histologic chorioamnionitis ranged from 66% at 20 to 24 weeks of gestation (n=261 neonates) to 16% at 34 weeks (n=770 neonates). The overall incidence was 31% (n=3928 neonates). At 25 to 29 weeks of gestation, neonatal survivors had a higher incidence of histologic chorioamnionitis (P=.02; 95% CI, 1.02-1.21). In addition, neonatal survivors had a higher incidence of a histologic fetal response to chorioamnionitis at 25 to 29 weeks of gestation (P=.01; 95%CI, 0.33-0.86) and 30 to 34 weeks of gestation (P=.02; 95%CI, 0.18-0.85).
Conclusion: Histologic chorioamnionitis is inversely related to gestational age. Both histologic chorioamnionitis and a histologic fetal response to chorioamnionitis were observed to be more common in preterm survivors of the neonatal period.