Anaemia

Anaemia is a condition where there is one or more of the following situations present:

• Reduction of the oxygen-carrying pigment, haemoglobin, in the blood.
• Reduction in the amount of circulating red blood cells (RBC).

There are several causes/types of anaemia, which include:

• Haemorrhage (blood loss) – iron deficiency anaemia.
• Haemolysis (increased destruction of RBC, which can be caused by toxins, an autoimmune response, the action of parasites, haemolytic disease of the newborn, Thalassaemia, Sickle Cell anaemia).
• Impaired production of RBC (iron deficiency anaemia, leukaemia, pernicious anaemia (AKA B12 deficiency) and folate deficiency).

Generally, symptoms of anaemia are similar for all types of the above, but with some variation. This section of the glossary will look at iron deficiency anaemia, as it is most relevant to childbearing.

Risk factors for iron deficiency include:

• Inadequate dietary intake of iron (vegetarians).
• Iron malabsorption, e.g. chronic diarrhoea, gastrectomy, malabsorption disease, such as coeliac disease.
• Pregnancy (increases the demand for iron).
• Blood loss, secondary to drug-induced gastrointestinal bleed (drugs involved include anticoagulants, aspirin, non-steroidal anti-inflammatories (NSAIDs) and steroids).
• Haemoglobinuria (presence of haemoglobin in urine).
• Blood loss (following trauma, menstruation).
• Mechanical RBC trauma (cardiopulmonary bypass, prosthetic heart valve, ventricular assist device).

Normal Pathophysiology of iron-deficiency anaemia:
Iron (Fe) is an essential component of haemoglobin – the red-pigmented oxygen-binder that makes up RBCs. A reduction in the amount of iron present results in the production of smaller RBCs, which are paler in colour. As a result, the RBCs cannot carry as much oxygen as normal. When the body’s stores of iron are used up, the concentration of transferrin (which binds with and transports iron) decreases.

In pregnancy, anaemia occurs in a different way. There is an increased need for iron, to supply the mother and fetus, but there is also a ‘relative’ reduction in the amount of circulating iron and RBCs. As pregnancy progresses, placental hormones bring about an increase in the amount of blood vessels in the woman’s body, which are needed to ensure that the uterus, placenta, lungs and breasts are well perfused. This causes a relative drop in blood pressure, as there is not as much relative fluid circulating through the system to keep these extra blood vessels supplied. To compensate, the woman produces more plasma, the liquid in which all components of the blood are transported, such as RBCs, white blood cells and platelets. In addition, the woman produces more RBCs (which is why it is important to ensure that the woman has good iron levels to begin with, to ensure she can supply the iron needed to create these extra RBCs). However, the amount of plasma produced is much greater than the amount of RBCs produced. There is a 50% increase in plasma volume, and only an 18% increase in red cell mass. As a result, there is ‘haemodilution’ (the blood is diluted) and so there appears a relative physiological anaemia, which is a normal part of pregnancy. There is some debate about the treatment of anaemia in pregnancy, as it is acknowledged that some degree of anaemia is normal. In fact, apparent anaemia can be a sign of excellent adaptation to pregnancy, with lower haemoglobin concentrations associated with higher birth weights, and higher haemoglobin concentrations associated with preterm birth and lower birth weight babies. The Word Health Organisation advise that haemoglobin levels should not fall below 11.0g/dL, and certainly haemoglobin concentrations of less than 10.5g/dL should be regarded as abnormal. At this stage, treatment of anaemia is normally commenced, by iron supplementation with ferrous sulphate and/or diet.

Blood values


(Medforth, Battersby, Evans, Marsh and Walker, 2006).

Explanation of terms above:
Haemoglobin – The concentration of the protein pigment of haemoglobin in the blood (grams per 100ml of blood).
Haematocrit (packed cell volume) – The percentage of total blood volume occupied by the red blood cells.
Red Cell Count – The number of red blood cells in the blood (number of thousand million per litre).
Other values of interest may include:
MCV (mean cell volume) – The size of the cell, or average volume of red cells. In iron-deficiency anaemia, this result is normally smaller, as the RBCs produced don’t have all the haemoglobin required. In physiological anaemia, this result should remain within normal ranges.
MCHC (mean cell haemoglobin concentration) – The average concentration of haemoglobin in red cells. This result is normally lower in iron deficiency anaemia.
Serum ferritin is a good indicator of how severe iron-deficiency anaemia is, as it illustrates the amount of iron stores available in the body. If haemoglobin levels are low, but serum ferritin levels are normal, usually this means that the anaemia is not pathological. In the first trimester in pregnancy, it is especially a good indicator of anaemia. However, in the second and third trimesters, the result will fall, independent of iron stores.


Signs and Symptoms of Anaemia:
Asymptomatic if anaemia is gradual in onset.
A blood test may first detect the problem.
General fatigue and weakness.
Headaches.
Pallor.
Tinnitus.
Lightheadedness.
Near syncope (fainting).
Dyspnoea on exertion (difficult in breathing).
With progression of anaemia, the individual may experience shortness of breath at rest, with Tachycardia/cardiac arrhythmia and palpitations.

Medforth, J., Battersby, S., Evans, M., Marsh, B. and Walker, A. (2006) Oxford Handbook of Midwifery. Oxford: Oxford University Press.

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