ABO phenotype and other risk factors associated with chorioamnionitis.

OBJECTIVE: To examine risk factors associated with chorioamnionitis.

STUDY DESIGN: We conducted a retrospective cohort study using data on women who delivered prematurely (< 37 weeks of gestation) over a 12-year period. Eleven potential risk factors were identified. Subjects were stratified according to their blood type into 2 groups: group 1, subjects with anti-B antibodies (blood types A and O), and group 2, subjects without anti-B antibodies (blood types B and AB). Univariate, bivariate, and logistic regression analyses were done to examine risk factors for chorioamnionitis while controlling for confounders.

RESULTS: The study included 2879 subjects, 96 of whom (3.3%) were diagnosed with chorioamnionitis. Chorioamnionitis increased significantly with alcohol use (adjusted odds ratio [AOR] = 4.7), prolonged rupture of membranes (ROM) (AOR = 4.16), anemia (AOR = 2.17), and group 1 status (AOR = 1.88). Advanced maternal age was protective of chorioamnionitis (AOR = 0.96).

CONCLUSION: Alcohol consumption during pregnancy, prolonged ROM, anemia, and blood types A and O are associated with increased risk for chorioamnionitis; advanced maternal age, with decreased risk. Further studies are needed to determine the efficacy of early prenatal care in the control of anemia and to examine its affect on the incidence of chorioamnionitis.