A randomized double-blind controlled trial will be carried out in which young, nulliparous (having never given birth) women will be randomly assigned to receive weekly supplementation with either iron and folic acid or folic acid alone. Women will be followed-up weekly up to 18 months. Women who become pregnant will be followed-up until delivery. Malaria risk in both groups will be compared by assessing the prevalence of peripheral parasitaemia at the first antenatal clinic visit for pregnant women and at the end of the first malaria transmission season for non-pregnant women. The incidence of clinical malaria will be assessed by active and passive case detection throughout the follow-up period.

Inclusion Criteria:

• Female
• At least 15 and less than 25 years old at enrolment
• Never given birth
• Resident within the Demographic Surveillance System (DSS) area
• Willing to adhere to the study requirements (including weekly observed drug intake)
• Provision of written informed consent (if non emancipated minor by guardian/parent with minor's assent

Exclusion Criteria:

• No menses for >3 months and/or palpable uterus or positive pregnancy test if history unclear
• Concurrent enrolment in another study
• Intention to move out of the study area for more than 2 months within the next 18 months
• Any significant illness at the time of screening that requires hospitalization, including clinical signs of severe anaemia (conjunctival or mucosal pallor, tachycardia, respiratory distress)
• History or presence of major clinical disease likely to influence pregnancy outcome (sickle cell disease, diabetes mellitus, severe renal or heart disease, open tuberculosis, epilepsy)