Background – Anaemia is relatively common in pregnancy and the most common cause is iron deficiency. Despite lack of evidence on the most effective way to treat anaemia in pregnancy, it is often treated with high doses iron that may cause gastrointestinal side effects, interfere with mineral absorption and cause haemoconcentration. Both severe anaemia and haemoconcentration have been linked with adverse pregnancy outcomes.
Objective - To compare the efficacy and side effects of low dose vs. high dose iron supplements in treating anaemia in pregnant women.
Design – Double blinded randomised dose response trial. Eligible pregnant women with anaemia (haemoglobin <110g/l) at the mid-pregnancy routine blood test were randomly allocated to receive either 20mg, 40mg or 80mg of iron daily for 8 weeks. Iron status of the women was assessed at the end of treatment. Gastrointestinal side effects were assessed every 2 weeks. Information on pregnancy outcomes and pregnancy complications were collected from medical records.
Outcomes – A total of 180 women were enrolled and 179 completed the study. At the end of treatment there was a clear dose response of increasing Hb concentration with iron dose (111 ± 13g/L at 20mg/day, 114 ± 11g/L at 40 mg/day, 118 ± 13g/L at 80mg/day, P=0.015). However, the incidence of moderate anaemia (Hb<100g/L) or outcome of pregnancy did not differ between groups. Gastrointestinal side effects (including nausea, stomach pain and vomiting) also increased with iron dose (P<0.05). Similarly, there was a tendency for more women to have haemoconcentration, defined as Hb>130g/L, with increasing iron dose (4%, 7%, 13%, P=0.175).
Conclusions – Although high dose iron supplements are more effective in increasing Hb levels in pregnancy, they are associated with more gastrointestinal side effects and may also be associated with a higher risk of haemoconcentration. Further research is needed to determine the optimal levels of Hb in pregnancy and the most effective and safe dose of iron to treat anaemia in pregnancy.