Histologic chorioamnionitis, antenatal steroids, and perinatal outcomes.

OBJECTIVE: To determine the perinatal effects of histologic chorioamnionitis on preterm neonates and the effectiveness of antenatal steroids in the presence of histologic chorioamnionitis.

METHODS: We studied neonates at our institution who weighed 1750 g or less at birth from January 1990 through December 1997. The population was stratified primarily by presence of histologic chorioamnionitis and secondarily by exposure to antenatal steroids. Subgroups were compared by various perinatal outcomes and confounding variables. Student t test, chi(2), Fisher exact test, and logistic regression were used for analysis.

RESULTS: Among 1260 neonates entered, the placentas of 527 had evidence of histologic chorioamnionitis and 733 did not. Those with histologic chorioamnionitis had a lower mean gestational age, lower birth weight, and higher rate of major neonatal morbidities than those without it. After adjusting for confounding variables, histologic chorioamnionitis independently associated with lower gestational age, lower birth weight, and neonatal death. Among neonates exposed to antenatal steroids who had histologic chorioamnionitis, there was a significantly lower incidence of low Apgar scores (18% compared with 33.5%, P <.001), respiratory distress syndrome (RDS) (39.6% compared with 55.9%, P <.001), intraventricular hemorrhage and periventricular leukomalacia (21.9% compared with 36.9%, P <.001), major brain lesions (7.7% compared with 18.4%, P <.001), patent ductus arteriosus (14.8% compared with 23.7%, P =.018), and neonatal death (8.3% compared with 16.2%, P =.02), with no increase in rate of proven neonatal sepsis (18.3% compared with 14%, P =.24).

CONCLUSION: Histologic chorioamnionitis increases major perinatal morbidity through its association with preterm birth and is independently associated with neonatal death. In the presence of histologic chorioamnionitis, antenatal steroids significantly decreased the incidence of RDS, intraventricular hemorrhage and periventricular leukomalacia, major brain lesions, and neonatal mortality, without increasing neonatal sepsis.