Anaemia in Pregnancy

Anaemia is defined as a low concentration of haemoglobin in the blood. This is the result of an underlying disease and is not a disease itself. The prefix an- means without, and the suffix –aemia relates to blood.

Haemoglobin is a protein found in red blood cells. It is responsible for picking up oxygen in the lungs and transporting it to the cells of the body. Iron is an essential ingredient in creating haemoglobin and forms part of the structure of the molecule.

Women are routinely screened for anaemia twice during pregnancy:

  • Booking clinic
  • 28 weeks gestation

 

During pregnancy, the plasma volume increases. This results in a reduction in the haemoglobin concentration. The blood is diluted due to the higher plasma volume.

It is important to optimise the treatment of anaemia during pregnancy so that the woman has reasonable reserves, in case there is significant blood loss during delivery.

 

Presentation

Often anaemia in pregnancy is asymptomatic. Women may have:

  • Shortness of breath
  • Fatigue
  • Dizziness
  • Pallor

 

Investigations

The normal ranges for haemoglobin during pregnancy are:

Time

Haemoglobin Concentration

Booking bloods

> 110 g/l

28 weeks gestation

> 105 g/l

Post partum

> 100 g/l

 

The mean cell volume (MCV) can indicate the cause of the anaemia:

  • Low MCV may indicate iron deficiency
  • Normal MCV may indicate a physiological anaemia due to the increased plasma volume of pregnancy
  • Raised MCV may indicate B12 or folate deficiency

 

Women are offered haemoglobinopathy screening at the booking clinic for thalassaemia (all women) and sickle cell disease (women at higher risk). Both are causes of significant anaemia in pregnancy.

Additional investigations are not routinely performed, by may help establish the cause of the anaemia. They may include:

  • Ferritin
  • B12
  • Folate

 

Management

Iron

Women with anaemia in pregnancy are started on iron replacement (e.g. ferrous sulphate 200mg three times daily). When women are not anaemic, but have a low ferritin (indicating low iron stores), they may be started on supplementary iron.

 

B12

The increased plasma volume and B12 requirements often result in a low B12 in pregnancy. Women with low B12 should be tested for pernicious anaemia (checking for intrinsic factor antibodies).

Advice should be sought from a haematologist regarding further investigations and treatment of low B12 in pregnancy. Treatment options for low B12 are:

  • Intramuscular hydroxocobalamin injections
  • Oral cyanocobalamin tablets

 

Folate

All women should already be taking folic acid 400mcg per day. Women with folate deficiency are started on folic acid 5mg daily.

 

Thalassaemia and Sickle Cell Anaemia

Women with a haemoglobinopathy will be managed jointly with a specialist haematologist. They require high dose folic acid (5mg), close monitoring and transfusions when required.

 

Last updated September 2020
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