The trial will be conducted in two maternity clinics in Ouidah, 40km from Cotonou. A total of 1600 women will be selected and randomised to receive either SP (1500 mg sulfadoxine with 75 mg pyrimethamine) or MQ (15 mg/kg) twice during pregnancy at ante-natal clinic (ANC) visits. The first dose will be given between 16 and 28 weeks of gestation, the second between 30 and 36 weeks, and at least one month after the first dose. Women will be visited at home within one week after the initial and subsequent ANC visits to check for adverse reactions due to the study drugs. Peripheral blood samples will be collected on each ANC visit to assess for haemoglobin level and parasitemia. Peripheral, placental, and cord blood samples will be collected at delivery for haematological determinations and parasitological examination. Birthweight will be recorded and the gestational age assessed by the Ballard method. The mother and her child will be assessed for general health status six weeks after birth.