Background Pregnant women, particularly during the first and second pregnancy, have a high risk of Plasmodium falciparum infection and these infections are often asymptomatic but lead to maternal anaemia and low birth-weight. One approach to preventing malaria in pregnancy is prompt effective management of clinical malaria. In areas of moderate and high transmission however, peripheral parasitaemia is not a sensitive indicator as many women with placental parasitaemia may not have peripheral parasitaemia. Another option is to administer full curative doses of an effective antimalarial drug at predefined intervals during pregnancy (IPTp) without screening for parasitaemia. The efficacy of IPTp has been studied mostly in areas of high perennial transmission in Kenya and Malawi. IPTp has however been little investigated in West Africa where transmission is often intense and highly seasonal. It may not be appropriate to translate results between areas with different ranges of transmission intensities across the sub-Saharan African region and there is a need to study the effect of IPTp in highly seasonal intense transmission areas in West Africa.