Pregnancy

Anaemia in pregnancy

Iron deficiency is the most common deficiency state in the world, affecting more than 2 billion people globally. Although it is particularly prevalent in less-developed countries, it remains a significant problem in the developed world, even where other forms of malnutrition have already been almost eliminated. Effective management is needed to prevent adverse maternal and pregnancy outcomes, including the need for red cell transfusion.

Anaemia is defined by Hb <110g/l in first trimester, <105g/l in second and third trimesters and <100g/l in postpartum period. For anaemic women, a trial of oral iron should be considered as the first line diagnostic test, whereby an increment demonstrated at two weeks is a positive result.

Once Hb is in the normal range supplementation should continue for three months and at least until 6 weeks postpartum to replenish iron stores.

Iron deficiency and anaemia

Iron deficiency represents a spectrum ranging from iron depletion to iron deficiency anaemia. In iron depletion, the amount of stored iron (measured by serum ferritin concentration) is reduced but the amount of transport and functional iron may not be affected.

Those with iron depletion have no iron stores to mobilize if the body requires additional iron. In iron-deficient erythropoiesis, stored iron is depleted and transport iron (measured by transferrin saturation) is reduced further; the amount of iron absorbed is not sufficient to replace the amount lost or to provide the amount needed for growth and function. In this stage, the shortage of iron limits red blood cell production and results in increased erthryocyte protoporphyrin concentration.

In iron-deficiency anaemia, the most severe form of iron deficiency, there is shortage of iron stores, transport and functional iron, resulting in reduced Hb in addition to low serum ferritin, low transferrin saturation and increased erythrocyte protoporphyrin concentration.

Effects on the fetus and infant

The fetus is relatively protected from the effects of iron deficiency by upregulation of placental iron transport proteins (Gambling et al, 2001) but evidence suggests that maternal iron depletion increases the risk of iron deficiency in the first 3 months of life, by a variety of mechanisms (Puolakka et al, 1980, Colomer et al, 1990).

Impaired psychomotor and/ or mental development are well described in infants with iron deficiency anaemia and may also negatively contribute to infant and social emotional behaviour (Perez et al, 2005) and have an association with adult onset diseases, although this is a controversial area (Beard et al, 2008; Insel et al, 2008).

Effects on pregnancy outcome

There is some evidence for the association between maternal iron deficiency and preterm delivery, (Scholl et al, 1994), low birth weight (Cogswell et al, 2003), possibly placental abruption and increased peripartum blood loss (Arnold et al, 2009). However further research on the effect of iron deficiency, independent of confounding factors, is necessary to establish a clear causal relationship with pregnancy and fetal outcomes.

(UK guidelines on the management of iron deficiency in pregnancy, British Committee for Standards in Haematology.)

More Info