Date Published: September 05, 2012
Publisher: The American Society of Tropical Medicine and Hygiene
Author(s): Machteld E. Boel, Marcus J. Rijken, Mupawjay Pimanpanarak, Naw Lily Keereecharoen, Stephane Proux, François Nosten, Rose McGready.
In a few small studies an association between blood group O and placental malaria has been described. The relationship between blood group and malaria in pregnancy (Plasmodium vivax and Plasmodium falciparum) was analyzed in 1,468 women from three longitudinal cohort studies in which weekly malaria screening was done systematically during pregnancy. One-third of women (447 of 1,468) had at least one malaria infection in pregnancy. The ABO blood group phenotype was not associated with the species of infection, frequency of malaria attacks, symptoms of malaria, hematocrit, or parasitemia during pregnancy.
Only a few studies have addressed the association between the ABO blood group system and malaria during pregnancy. Four studies from Africa (Gabon,1 The Gambia,2 Malawi,3 and Sudan4) were recently reported in a single work (the total number of women studied was 1,516: 378, 198, 647, and 293 women respectively).1 In The Gambia and Malawi, blood group O conferred a higher risk of active placental infection in primipara, but a significantly lower risk in multipara. These findings were not confirmed by the study from Gabon, in which no statistically significant risk of placental parasitemia was observed in any blood group.1 In another study in Sudan no association was found between blood group and active placental infection, which was observed in 18 of 236 women studied.5 We were unable to find any published reports from Asia. We determined the relationship between blood group and malaria (Plasmodium vivax and Plasmodium falciparum) in pregnancy and pregnancy outcome analyzing longitudinal data from three cohort studies in which regular malaria screening was done systematically during pregnancy.
On the western border of Thailand, the Shoklo Malaria Research Unit has been conducting weekly antenatal clinics (ANC) since 1986. It has six established clinics that provide antenatal care and three clinics with delivery services for migrant workers and refugee populations from Myanmar. All pregnant women are encouraged to attend ANC on a weekly basis for malaria screening and early diagnosis and treatment, because there is no drug available for intermittent preventive treatment in this area of multi-drug resistant malaria.6
Of the 1,570 women included in the three cohorts 1,468 (93.5%) had a blood group phenotype available: group O was the most prevalent and group AB the least prevalent (Table 1). The 6.5% (102 of 1.570) of women who did not have blood group tested had a lower median number of antenatal visits (12 [1–32] versus 22 [1–41], P < 0.001), and were less likely to have been followed up until delivery (58% [59 of 102] versus 4% [62 of 1,468], P < 0.001) compared with women who were tested. Out of 1,468 women 447 (30.4%) had at least one malaria episode during pregnancy, and there was no significant difference in the proportion of women with malaria in the different blood groups (Table 2). The number of women with uncomplicated P. falciparum hyperparasitemia (eight cases), or severe P. falciparum malaria (one case), were so low that statistical comparisons were not performed. Of the 54% (793 of 1,570) women who delivered in the Shoklo Malaria Research Unit (SMRU) clinic, 487 (61.4%) placenta samples were available. Only 5 placentas (1.0%) were malaria positive: for blood group O 0.5% (1 of 205), A 0.9% (1 of 110), B 2.2% (3 of 137), and AB none of 35. Of the women who had malaria during pregnancy the proportion infected with different species was not significantly different between blood groups and this non-significant association was maintained when comparing symptomatic malaria infection, the median number of infections of P. falciparum or P. vivax, the geometric mean maximum parasitemia of P. falciparum or P. vivax, or the mean hematocrit at the time of P. falciparum or P. vivax (Table 3). This is the first study to examine the relationship between ABO blood group phenotype in women prospectively and actively followed for malaria (P. falciparum and P. vivax) during pregnancy. There was no indication from this large cohort where nearly one-third of women were diagnosed with malaria during pregnancy that ABO blood group phenotype relates to 1) the species of infection, 2) frequency of malaria attacks, 3) symptoms of malaria, 4) hematocrit, and 5) parasitemia. This absence of association remained true within each gravida group. Source: http://doi.org/10.4269/ajtmh.2012.12-0129