Compliance statements:
  1. We, the authors, Disclosure no conflict of interests. This includes: relevant financial, personal, political, intellectual or religious interests.
  2. All authors contributed equally to the final manuscript. TS, JL, and DWT performed the data analysis. DWT, DT-J and JL formulated the study concept. All authors (TS, JL, DT-J and DWT agreed the final manuscript prior to submission.
  3. Ethics approval was not required since the study was a retrospective analysis of data already collected and used for the purposes of the UK National Antenatal Haemoglobinopathy screening programme. No additional blood samples were required for the study.
  4. The study was not funded.
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2) WHO Guideline 2016: DAILY IRON SUPPLEMENTATION IN ADULT WOMEN AND ADOLESCENT GIRLS
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