The relationship between fetal ABO and Rhesus blood groups and the development of pre-eclampsia: a retrospective case control study

Objective: The objective was to study the relationship between fetal ABO and Rhesus blood groups and the development of pre-eclampsia (PE). Study design: This was a retrospective case control study conducted in a large public healthcare provider in Doha, Qatar. The study group consisted of 254 consecutive pregnancies with the diagnosis of PE, from the cohort of more than 18000 deliveries conducted in 2014. The control group consisted of 500 consecutive uncomplicated deliveries in the same year. Patient demographic data, maternal and fetal bloods types were collected from patient electronic medical records. Comparative analysis was done using Chi Square, Student t and Mann-Whitney tests, as applicable. The main outcome measure was the percentage of fetal ABO and Rhesus groups in the study and control groups. The secondary outcomes looked at were the distribution of maternal ABO and Rhesus groups among the groups, and the effect of maternal-fetal blood type interrelationship on the occurrence of PE. Results: There was no significant association noted between fetal blood groups and PE. More women in the PE group were Rhesus negative (5.9% vs 2.2% OR:2.8, 95% CI: 1.3-6.2, p=0.011). In the PE group, mothers who were Rhesus negative were found more likely to have Rhesus positive fetuses (OR:13.33, 95% CI: 1.32 to 134.6, p=0.0281). There was a decrease in PE with maternal group B and fetal group O (OR:0.3, 95% CI: 0.11-0.84, p=0.021) and an increase in PE with maternal group O and the fetal group O (OR:1.73, 95% CI: 1.05-2.85, p=0.031). Conclusion: No association has been found between fetal blood group and PE; however maternal-fetal Rhesus and ABO disparity seems to affect the incidence of PE, particularly a Rhesus negative woman with a Rhesus positive fetus. There is a need for larger prospective studies to confirm an association.