Iron deficiency anaemia is a common disorder affecting up to 30% of pregnant women. Treatment guidelines for iron deficiency anaemia in pregnancy exist, which if adopted, can reduce the associated risks of maternal and fetal morbidity and mortality. Objective: To optimise the implementation of the British Society of Haematology (BSH) guidelines, for the treatment of iron deficiency anaemia (IDA) in pregnancy, assessing response rates and predictability of response. Study population: A prospective cohort study of pregnant women with IDA at a single site. Methods: Women with anaemia were offered follow-up through a dedicated anaemia clinic. First line treatment was with ferrous sulphate 200mg three time a day as per earlier BSH guidelines. The response was assessed 2 to 4 weeks later by measuring the haemoglobin (Hb) concentration. A response was defined in 2 ways; i) a haematological response (HRes), a 10g/L increase in Hb and ii) adjusted obstetric response (ORes), a 10g/L increase in Hb and/or gestationally adjusted normalisation of the Hb. Education and advice were provided to women, with on-going follow-up at clinic appointments including an assessment of side effects. Continuing non-response led to an offer of intravenous iron infusion (IVI). Following a response with oral iron, treatment was continued for a further 3 months when the women were again reviewed. Results: The initial rate of HRes to a first course of oral iron was 36.5% and for ORES at 55.2%. At the end of all follow up, post-delivery, the HRes rate was 70.5% and ORes 88.5% (excluding 9 women lost to follow up). Responders (HRes) to oral iron had lower median Hb at diagnosis 95g/L compared to non-responders 100g/L. The responders median Hb was 113g/l versus 103g/L for non-responders at first follow-up and was Hb 122g/L versus 110 g/L, respectively, at the end of the study. The same pattern was seen for ORes. Non-responders reported more side effects than responders 15% versus 5% respectively. Logistic modelling suggested Hb at diagnosis, ethnicity, trimester at recruitment, marital status and parity had a predictive accuracy for a response of 75%. The specificity was high 89.8% but sensitivity low 42.9%. Conclusion: Oral iron treatment for IDA in pregnancy is challenging to deliver due to side effects and poor adherence, despite national guidelines. High rates of non-response were seen even in the setting of a specialist anaemia clinic. Alternative strategies such as prevention of IDA need to be evaluated.