All women who attended one of the study clinics during the trial period and who were multigravidae were asked if they wished to join the study. If this was the case, an initial screening questionnaire was administered to assess their suitability to do so. Eligibility criteria were - a pregnancy of more than 15 weeks gestation, a hemoglobin (Hb) concentration of more than 7 g/dL, absence of a history of sensitivity to sulfonamides and absence of any chronic underlying illness.