(Collaborators: Alexandre Manirakiza, Sandrine Moussa, Aude Boulay, Olga Sakanga, Sébastien Breurec, Mirdad Kazanji(IP Bangui), Lenaig Le-Fouler, Muriel Vray (IP Paris)). Funding : Fondation de France. Accounting for HIV serological status in patients is critically important for effective malaria prevention. CTX is recommended for preventing opportunistic infections in HIV positive women with CD4 count < 350 clls/mm3. The efficacy of CTX as a prophylaxis for P. falciparum malaria is well known. A clinical trial (CTX versus SP) undertaken among children in Bandiagara, Mali reported a protective efficacy of 99.7%. The WHO and the Central African Republic (CAR) recommend intermittent SP as malaria prophylaxis for pregnant women. Therefore it is superfluous and contraindicated to provide SP and CTX together in HIV-positive persons when CD4 is <350 cells/mm3. In contrast, few studies until now have described the efficacy of CTX in the prevention of malaria among pregnant women, and particularly its efficacy in an environment in which frequent therapeutic failures of SP are on the rise, as is the case in the CAR. Finally, although existing studies have not confirmed this hypothesis, there remain persistent concerns about the possible development of cross-resistance in P. falciparum to both CTX and SP because of their similar modes of action. The principal objective of this randomized, open label trial, carried out under real-life conditions of care, is to demonstrate the superiority of CTX (administered as a daily dose until childbirth) over SP (administered as directly observed treatment of three doses) on placental malaria parasitaemia in HIV-positive pregnant women whose CD4 count > 350 cells/mm3. This study will also permit to compare the two treatments in terms of the incidence of malaria episodes during pregnancy, profiles of resistant parasites isolated during these malaria episodes and in the placenta during childbirth, material anemia, birth weight, and infant anemia. An evaluation of adherence to the CTX treatment will be conducted at each prenatal visit; women included in the trial will be asked to report the number of pills remaining in their possession. We plan to recruit 150 women in each group. Expected results The principal hypothesis is that CTX is more efficacious than SP on placental malaria parasitaemia. This result could be explained by higher plasma levels among those taking CTX. The verification of this hypothesis will permit the recommendation of CTX as a prophylactic treatment for malaria among HIV-positive women, regardless of CD4 count.