Iron levels in pregnancy, physiology or pathology? Assessing the need for supplements

This paper re-examines the need for iron supplements among pregnant women by considering whether the changes they experience in iron levels are physiological or pathological. The literature reveals that changes in the blood leading to haemodilution are necessary adaptations to healthy pregnancy. These changes alter normal haematological values. Consequently, indices such as haemoglobin concentration lose their accuracy as measurements of iron status. Tests for iron stores such as serum ferritin are more likely to prove useful indicators of deficiency. Iron stores are greatly depleted early in pregnancy, whether or not supplements are taken, when absorption is low. They return to pre-pregnant levels quickly after delivery. Reasons for these phenomena are postulated. High levels of haemoglobin in pregnancy seem to be as undesirable as very low levels. As proved benefits from iron therapy are few, it is questionable whether the antenatal period is an appropriate time to supplement. However, the issue of physiology versus pathology remains unresolved. Pregnancy is assumed to be an abnormal variation of the non-pregnant state; its parameters being judged against those of the population at large. As most pregnancies form a normal part of a woman's life cycle, the physiological ranges for pregnancy itself need to be determined.