Anaemia in pregnancy--not just iron deficiency.

Approximately one third of pregnant women in Vietnam have been previously estimated to be anaemic [1] . In this issue of Acta Haematologica , Siridamrongvattana et al. [4] report in a cross-sectional study of 399 women in the first trimester of pregnancy in central Vietnam that they found an unexpectedly low prevalence of anaemia (19.3%), iron deficiency (20.1%) and iron-deficiency anaemia (6%). Interestingly, the authors also found that most of the burden of anaemia could not be explained by iron deficiency: 31% of anaemic women had iron deficiency (ferritin <15 μg/l), 26% were found to have a thalassaemia mutation, and the remaining 43% of anaemic women had apparently replete iron stores and no evidence of haemoglobinopathy. There were no cases of severe anaemia. Inflammation did not appear to play a role. Other haematinic micronutrients (i.e. vitamins B12 and A, folate) were not measured. These findings raise several interesting and important questions. Firstly, what is causing the unexplained anaemia? Other haematinic micronutrient deficiencies may account for some of these cases. Another possibility is that the authors’ definition of iron deficiency is too specific, and that anaemic women with higher ferritin concentrations still have depleted iron stores. A study in nonpregnant women of reproductive age in Vietnam indicated that 77% of women who achieved an appropriate haemoglobin response to iron supplementation had a ferritin level <30 μg/l [5] , suggesting a higher cut-off for ferAnaemia remains an important global health problem. Almost 42% of all pregnant women worldwide (56 million) are thought to be anaemic. The prevalence is highest in low-income countries, especially in South and South East Asia, and Sub-Saharan Africa [1] . Iron deficiency is often considered the chief cause, and often deemed synonymous with anaemia in the public health context. For example, WHO guidelines assume that at least half the worldwide burden of anaemia is attributable to iron deficiency [2] . Indeed, the most recent global burden of disease report conflates iron deficiency with anaemia, using haemoglobin measurements to define the burden of disease attributable to iron deficiency [3] . However, beyond iron deficiency, anaemia has many possible causes. In the public health context, inherited red cell disorders, particularly thalassaemia and haemoglobinopathy (e.g. HbE) carrier and compound heterozygous and homozygous states, infections (especially malaria) and inflammation, and other micronutrient deficiencies (i.e. deficiencies of folate and vitamin B12 and A), may be important depending on the geographic setting and the population. Distinguishing these causes requires clinical observation and expensive laboratory investigation and, thus, relatively few studies have undertaken detailed analysis of the determinants of anaemia in populations. However, it is interesting that, where these have been performed, iron deficiency is sometimes a surprisingly minor player. Received: April 25, 2013 Accepted after revision: May 13, 2013 Published online: August 20, 2013