Case-control study of maternal blood group and severe pre-eclampsia.

The relation of maternal blood group to pre-eclampsia has not been adequately studied in previous research. To investigate this relation, we conducted a case-control study of primigravidae. Data on 204 consecutive severely pre-eclamptic patients delivered pre-term and 744 controls were analysed using multivariate methods. After adjustment for the confounding effects of maternal age, social class, origin, education, pre-pregnancy weight and body mass index, and weight gain in pregnancy, we found an increased risk of pre-eclampsia for mothers with blood type AB (adjusted odds ratio = 3.07; 95% confidence interval 1.48-6.36). With respect to blood group O, A, B and Rh type, no statistically significant correlation with severe pre-eclampsia was found. Although these results should be considered with caution, they support the hypothesis of a linkage mechanism involving blood group in the inheritance of susceptibility to pre-eclampsia.