Do Blood group and Sickle cell trait protect against placental malaria?

Blood group O is reported to confer some degree of protection from severe malaria in endemic setting. This protection is believed to be due to reduced and smaller rosette formation in people of blood group O which can easily be cleared by the host immune system. Also, sickle cell trait (HbAS) is reported to disrupt the adhesion of infected erythrocytes to microvascular endothelial walls, which could protect pregnant women from placental malaria. We determined the association between HbAS and ABO blood group, and placental malaria amongst pregnant women of all parities. The study enrolled 221 pregnant women. Peripheral blood samples were taken for malaria smears, ABO blood grouping and haemoglobin (Hb) electrophoresis. A structured questionnaire was used to age, bed net usage, and the number of Sulphadoxine-pyrimethamine (SP) doses taken by a pregnant woman. Two hundred and twenty-one (221) pregnant women were enrolled and out of this number, 110 (49.8%) were primiparae and 111 (50.2%) multiparae, with a mean age of 23.7±5.2. Placental malaria (PM) prevalence by PCR detection was 19.4% (43/221). Of those who were malaria positive 58.1% (25/43) were primiparae. Primiparae who are of blood group O were more susceptible to PM [P=0.04, (OR); 2.85, 95% (Cl), 1.12-9.01]. But sickle cell trait did not reduce the prevalence of PM [P=0.84 (OR); 0.92, 95% (Cl), 0.43-1.99]. Non-blood group O primiparae women were protected against placental malaria. This could be why some primiparae women are protected from PM, just like multiparae women.