Anaemia in pregnancy

Summary

• Anaemia in pregnancy is defined as a haemoglobin concentration of less than 10 gm/dl when the peripheral blood is examined.
• The most common cause of anaemia in pregnancy is lack of iron. Less often it is caused by folic acid deficiency.
• In some populations, 80% of pregnant women are anaemic.
• Those most at risk are women from low socio-economic groups, and teenagers.
• Anaemia is diagnosed by estimating the haemoglobin concentration and examining a peripheral blood smear for the characteristic red blood cell changes.
• Iron and folate supplementation is indicated during pregnancy

Definition

Anaemia during pregnancy is defined as a haemoglobin (the molecule which carries oxygen in the blood) concentration of less than 10 gm/dl.

Any patient with a haemoglobin of less than 11 gm/dl to 11.5 gm/dl at the start of pregnancy will be treated as anaemic. The reason is that as the pregnancy progresses, the blood is diluted and the woman will become anaemic. The dilution of blood in pregnancy is a natural process and starts at approximately the eighth week of pregnancy and progresses until the 32nd to 34th week of pregnancy.

Causes

The most common cause is iron deficiency. It usually occurs due to low iron stores prior to pregnancy. The growing foetus depletes what stores there are and takes priority for any iron available. It is important to remember that increased iron requirements continue after the birth of the baby due to blood loss and breastfeeding.

Less often, anaemia in pregnancy is caused by folic acid deficiency.

In certain populations, pregnancy can be complicated by sickle cell trait and anaemia, as well as thalassaemias. These diseases, in which the red blood cells are abnormal, present special problems in pregnancy.

Who is affected and who is at risk?

In some populations, as many as 80% of pregnant women are anaemic. They are generally women from lower socio-economic groups in developing countries as well as pregnant teenagers.

Women who experienced heavy periods and those who became pregnant soon after the birth of a child are at particular risk of becoming anaemic in pregnancy.

Symptoms and signs

The symptoms such as tiredness and general weakness will be similar to those of any other type of anaemia. In severe cases, the woman will be short of breath even at rest.

If the anaemia is prolonged, other signs of iron-deficiency anaemia may develop such as a smooth shiny tongue and tenderness of the skin at the corners of the mouth. However, these advanced signs are rare.

Diagnosis

The diagnosis is made by examining a full blood count and noting the low haemoglobin concentration as well as the characteristic small, pale red blood cells under the microscope (in the case of iron deficiency anaemia).

The diagnosis of iron deficiency anaemia can be confirmed by measuring the amount of storage iron as well as the levels of iron binding proteins in the blood. The diagnosis of folate deficiency is confirmed by estimating the red blood cell folate levels.

If the anaemia does not respond to iron treatment, additional folic acid deficiency should be suspected.

Prevention

A well balanced diet is always recommended but iron and folate supplementation is indicated in pregnancy.

Treatment

When the anaemia is caused by lack of iron, it is treated with iron supplements, preferably ferrous sulphate tablets (300mg). These supplements should not be taken more than twice daily, since the side effects of iron are increased in doses of more than two daily. The side effects are stomach upsets and constipation which are problematic in pregnancy.

If the anaemia is due to folic acid deficiency, it is treated with folic acid supplements (1 to 5 mg once a day).

Outcome

As long as the anaemia is treated and corrected, there should be no problems.

When to call your doctor

All pregnant women should be fully assessed at the start of their pregnancy so that any problems such as anaemia will be picked up and treated.

Reviewed by Dr Betsie Lombard