Malaria is a major contributor of disease burden in Sub-Saharan Africa: 90% of global cases occur there, and pregnant women and children under 5 years are the most vulnerable. Malaria in pregnancy increases risks of abortion, stillbirth, prematurity, intrauterine growth retardation and maternal anemia, and is associated with higher risk of low birth weight and perinatal, neonatal and infant mortality. For prevention and control of malaria in pregnancy, the WHO recommends Intermittent Preventive Treatment (IPT) with antimalarial drugs, insecticide treated nets (ITNs) and effective treatment of malaria and anemia.

HIV in pregnancy increases the risks of malaria, and it seems that the efficacy of IPT with the drug sulphadoxine-pyrimethamine (SP) is decreased in HIV+ pregnant women.

Malaria prevention in pregnancy in Zambia relies on ITNs and IPT with SP. Daily prophylaxis with cotrimoxazole (CTX) effectively reduces mortality and morbidity in HIV+ individuals, and antibiotic therapy during pregnancy might help to decrease adverse pregnancy outcomes. CTX prophylaxis improves birth outcomes in HIV+ women with CD4<200/µl: a study concluded that antenatal provision of CTX was beneficial for HIV+ pregnant women with low CD4 but not in women with ≥200/µl (however, this study was carried out in an area with very low risk of malaria , and CTX may have a different effect depending on endemic conditions). The WHO recommends daily CTX in addition to ARVs, to prevent opportunistic infections in all HIV+ patients.

Concurrent administration of SP and CTX may increase the incidence of severe adverse reactions in HIV+ patients, so WHO has promoted CTX prophylaxis as an alternative to SP for the IPT in immuno-compromised pregnant women. Unfortunately, there is insufficient information on the effectiveness of daily CTX for preventing malaria infection in pregnancy: so, SP is still the only antimalarial recommended by WHO for this purpose. With the increase in SP resistance and with the newer antimalarials still being studied for safety and efficacy in pregnancy, CTX could be an alternative for SP in reducing malaria and malaria-related morbidity and mortality in pregnancy.

This study will try to to see if in HIV- and HIV+ pregnant women, CTX is not inferior to SP in reducing placental parasitaemia. Such information is needed to issue updated, effective guidelines on malaria prevention in pregnancy

Malaria is a major contributor of the disease burden in Sub-Saharan Africa: some 90% of global cases occur in Sub-Saharan Africa, with pregnant women and children < 5 representing the most vulnerable population. P.falciparum infection in pregnancy leads to parasite sequestration in the maternal placental vascular space, causing increased risks of abortion, stillbirth, prematurity, intrauterine growth retardation and maternal anaemia; it is also associated with increased risk of low birth weight (LBW) and perinatal, neonatal and infant mortality.In low transmission areas, malaria can be severe with a high risk of maternal and perinatal mortality (up to 60-70%). In highly endemic areas, malaria is still associated with maternal anaemia, LBW and stillbirth. For prevention and control of malaria in pregnancy, the WHO recommends Intermittent Preventive Treatment (IPT), insecticide treated nets (ITNs) and effective case management for malaria and anaemia.

HIV-1 infection in pregnancy increases the risks of malaria. In HIV+ pregnant women, in addition, the efficacy of IPT with sulphadoxine-pyrimethamine (SP) appears decreased.

In Zambia, the malaria incidence rate increased from 121.5/1000 in 1976 to 482.0/1000 in 2003. The high rates were predominantly evident among pregnant women and children \

Inclusion Criteria:

• Confirmed pregnancy (through palpable fundus and/ or positive pregnancy test)
• Gestational age between 16 and 28 weeks
• Hb > 7 g/dl, by Hemocue
• No symptoms consistent with malaria
• Residence within the health facility catchment's area
• Willingness to deliver at the health facility
• Willingness to adhere to all requirements of the study (including HIV-1 voluntary counselling and testing)
• Ability to provide written informed consent. If the woman is a minor of age/not emancipated, the consent must be given by a parent or legal guardian according to national law (however, in this case, also the minor woman will sign the consent form, to document that she is freely giving her assent to take part in the study).

Exclusion Criteria:

• History of allergy to study drugs, or previous history of allergy to sulpha drugs
• History or presence of major illnesses likely to influence pregnancy outcome including diabetes mellitus, severe renal or heart disease, or active tuberculosis
• Any significant illness at the time of screening that requires hospitalization
• Intent to move out of the study's catchment area before delivery or deliver at relative's home out of the catchment's area;
• Prior enrolment in the study or concurrent enrolment in another study
• Severe anaemia (Hb<7 g/dl)
• Previous history of unfavourable pregnancy outcome: pre-eclampsia, caesarean section, stillbirth.
• Eligible HIV-positive women who, following the National guidelines, have to be put on CTX prophylaxis (e.g. having a CD4 count <350/µl) or already on CTX and/or ARV treatment will be excluded from the RCT but included in a prospective observational cohort and receive 2 tablets of CTX daily