Association between maternal ABO blood group and preeclampsia: a prospective cohort study

Background: Preeclampsia is a leading cause of maternal morbidity and mortality. Various predictive methods exist, but none are without flaws. Risk factors vary in different women and at different gestational ages; hence, investigating non-modifiable factors, such as ABO and Rhesus blood groups, may aid prediction and early detection of preeclampsia. Objectives: This study aimed to evaluate the association between maternal ABO blood groups and preeclampsia. Design: This was a prospective cohort study. Methods: This study included singleton, normotensive, Rhesus-positive primigravidae with different ABO blood groups at <20 weeks of gestation. The primary outcome was the incidence of preeclampsia in mothers with Rhesus (D)-positive ABO blood groups (O, A, B and AB), while the secondary outcomes were the overall preeclampsia incidence and the odds ratio for preeclampsia between blood group O and non-O (A, B and AB) participants. Results: A total of 264 participants were enrolled, with 244 followed up until delivery. Eighteen participants developed preeclampsia with an incidence of 7.4% (95% confidence interval: 3.9–10.7). Most participants had blood group O (57.0%), followed by A (29.5%), B (12.7%) and AB (0.8%). The mean gestational age at preeclampsia onset was 37.8 ± 2 weeks. Blood group AB had the highest incidence of preeclampsia (50%), followed by B (16.1%), O (5.8%) and A (5.6%). Among 105 participants with non-O blood groups, 10 developed preeclampsia ( p  = 0.265). The adjusted odds ratio for the non-O blood group who developed preeclampsia was 1.65. Conclusion: Maternal ABO blood group was not significantly associated with preeclampsia incidence. However, blood group AB exhibited the highest preeclampsia incidence compared with the other blood groups.