Plasmodium falciparum resistance to chloroquine (CQ) and sulfadoxine-pyrimethamine (SP) continue to spread, impeding control of this important disease. CQ and SP are still the most commonly used antimalarial drugs for malaria prevention during pregnancy and might be made less effective by resistance. However, the treatment and prophylaxis regimens used may also create conditions for selecting resistant malaria parasite strains. A better understanding of the relationships between chemoprophylaxis regimens and resistance would be helpful to improve chemoprophylaxis of malaria in pregnancy.