Histologic evidence of inflammation and risk of placental abruption.

OBJECTIVE: The objective of the study was to determine whether placental abruption is associated with an increased incidence of histologic chorioamnionitis among singleton gestations and whether this association is dependent on its severity.

STUDY DESIGN: Data were derived from the New Jersey-Placental Abruption Study, an ongoing, multicenter, case-control study conducted in New Jersey since August 2002. Subjects were women with a clinical diagnosis of abruption, and controls were matched to cases based on parity and maternal race/ethnicity. Two perinatal pathologists, blinded to the case-control status, performed all histologic examination based on standardized protocol. The association between chorioamnionitis and abruption was quantified based on odds ratio (OR) with 95% confidence interval (CI), after adjustment for potential confounders, and all analyses were stratified based on preterm birth (less than 37 weeks) status.

RESULTS: At preterm gestations (n = 141), chorioamnionitis was present in 30.8% and 12.5% of abruption cases and controls, respectively (OR 3.6, 95% CI 1.7 to 10.5). At term gestations (n = 205), the corresponding rates were 34.6% and 20.4%, respectively (OR 2.8, 95% CI 1.3 to 6.1). Severe chorioamnionitis was 7.2 (95% CI 1.6 to 20.1) and 18.3 (95% CI 2.2 to 150.4) times more common in abruption patients at preterm and term gestations, respectively.

CONCLUSION: Histologic chorioamnionitis is associated with placental abruption. The association was strongest in the presence of severe chorioamnionitis at term and, to a lesser extent, at preterm gestations. These observations suggest that the histologic findings in abruption are accompanied by severe inflammation, in both preterm and term gestations.