Women were allocated to receive SP (pyrimethamine 25 mg + sulfadoxine 500 mg)(Cosmos Pharmaceuticals, Nairobi) or matching placebo. An initial dose of SP or placebo (three tablets) was given at the time of enrolment into the trial and at all subsequent visits to the antenatal clinic up to a maximum of four treatments. All women were given iron and folic acid supplements as recommended by the Ministry of Health guidelines.