Background: Anaemia in pregnancy is a major health problem in many developing countries where nutritional deficiency, malaria and other parasitic infections contribute to increased maternal and perinatal mortality and morbidity.

Objectives: The objective of this review was to assess the effects of iron supplementation on haematological and biochemical parameters, and on pregnancy outcome.

Search strategy: The Cochrane Pregnancy and Childbirth Group trials register was searched. Study authors were also contacted.

Selection criteria: Acceptably controlled trials of iron supplementation for pregnant women.

Data collection and analysis: Eligibility and trial quality were assessed by one reviewer. Study authors were contacted for additional information.

Main results: Twenty trials were included. Iron supplementation raised or maintained the serum ferritin above 10 milligrams per litre. It resulted in a substantial reduction of women with a haemoglobin level below 10 or 10.5 grams in late pregnancy. Iron supplementation, however, had no detectable effect on any substantive measures of either maternal or fetal outcome. One trial, with the largest number of participants of selective versus routine supplementation, showed an increased likelihood of caesarean section and post-partum blood transfusion, but a lower perinatal mortality rate (up to 7 days after birth).

Reviewer's conclusions: Iron supplementation appears to prevent low haemoglobin at birth or at six weeks post-partum. There is very little information on pregnancy outcomes for either mother or baby. There are few data derived from communities where iron deficiency is common and anaemia is a serious health problem.