The use of monthly sulfadoxine-pyrimethamine (SP) compared to a standard 2-dose SP in HIV-positive pregnant women, resulted in non-significant reduction in maternal anemia (Hb<11g/dl) (RR 0.97, 95% CI0.84, 1.12), however, presence of malaria in the placental blood (placental parasitaemia) decreased (RR 0.42; 95% CI: 0.23, 0.76) [27]. This evidence concerns the gene GSTM1 and malaria.