This work aims to improve the use of chemoprophylaxis in pregnancy by determining whether there is a relationship between the use of standard prophylactic regimens with CQ and SP and the occurrence of P. falciparum resistant strains in pregnant women. The study consists of 2 parts. The first part is a randomized trial comparing 3 chemoprophylactic treatment groups: - weekly CQ after initial presumptive CQ treatment, - CQ intermittent presumptive treatment given as a standard dose at 2nd and 3rd trimester, respectively and SP intermittent presumptive treatment given as a single dose at 2nd and 3rd trimester, respectively. These treatment groups will also be compared to a group of women delivering at the same health centre but who have not been participating in the study. The second part will be a clinical trial for assessment of clinical and parasitological efficacy of CQ and SP treatment in pregnant women presenting with uncomplicated malaria attacks.