When a woman is pregnant, she may develop anaemia. And when she has anaemia, she may feel tired and her baby become very small and may be delivered earlier than expected. The most common cause of anaemia among pregnant women is iron deficiency anaemia.

During pregnancy, the body produces more blood to support the foetal growth. If the iron or B12 and folate supply are not adequate, red cells may not be produced enough to meet the demand. With the advancement of the pregnancy, blood volume increases, which results in a concomitant haemodilution. Although red blood cell (RBC) mass increases during pregnancy, plasma volume increases more, resulting in a relative or physiological anaemia.  In an iron-replete population, anaemia is defined as a haemoglobin level less than11 g/dL in the first trimester, 10.5 g/dL in the second trimester and 10 g/dL in the third trimester.

Causes Of Anaemia In Pregnancy

1. Iron deficiency Anaemia

   Iron deficiency anaemia accounts for 75-95% of the cases of anaemia in pregnant women. A pregnant woman often has insufficient iron stores to meet the demands of pregnancy. The pregnant women must be encouraged to add iron supplemnt to their diet. A full blood count should be done routinely during first visit to antenatal clinic. An MCV less than 80 fL and MCH less than 27 pg suggest the possibility of hypochromic microcytic anaemia. Severe anaemia (Hb less than 7g/dl) should be referred for investigation of the causes and treatment. Further studies should include iron study and haemoglobin analysis to look for iron deficiency or Thalassemia.

   Clinical symptoms of anaemia include fatigue, malaise, headache, palpitation, headache, giddiness and shortness of breath.

   The clinical consequences of anaemia include preterm delivery, perinatal death and postpartum depression. Foetal and neonatal consequences include low birth weight and poor mental and psychomotor performance.

   Routine iron supplementation is recommended in the model of routine antenatal care. The use of parenteral iron therapy for patients who are not able to tolerate oral iron therapy should only be done in the hospital setting. There are different preparations of parenteral iron therapy that doctors will discuss with the patient. There will be other alternative therapy that can elevate the haemoglobin level, namely blood transfusions.

2. Folate and vitamin B-12 deficiency anemia

   Folate deficiency is much less common than iron deficiency; however, folate supplement is recommended to all pregnant mothers to reduce the risk of neural tube defect. Folate and B12 deficiencies usually cause non-pernicious megaloblastic anaemia with MCV more than 100 fL. Usually combined deficiencies with iron will cause normochromic normocytic anaemia. If patient has low level of folate, she may require higher dose of folate.

   Patients with vitamin B-12 deficiency need further workup to determine the level of intrinsic factor to exclude pernicious anaemia. But some tests should be done after delivery as they may not be suitable during pregnancy e.g Schilling test because it involve the usage of radionuclide material

3. Infectious causes of anemia

   Infectious causes of anemia are more common in nonindustrialized countries. Anaemia can be caused by infections such as HIV, malaria, worm infestation, hepatitis and other rare organisms. If the patient’s history suggests exposure to any of these infectious agents, appropriate laboratory studies should be performed.

4. Thalassemia

   Thalassemia is a common disease. The disease is found throughout the world, but its highest prevalence is in areas endemic for malaria, where it may confer a protective advantage. These regions include the Mediterranean, central Africa, and parts of Asia. It is characterised by impaired production of one of the normal globin peptide chains found in haemoglobin (Hb). Healthy adults should have more than 95% haemoglobin A (HbA), which consist of 2 alpha and 2 beta peptide chains.

   There are two major types of thalassemia, alpha-thalassemia and beta-thalassemia which result from decreased production of one or more of these peptide chains. The clinical consequences can be ineffective erythropoiesis, haemolysis, and anaemia of varying degrees. A carrier of a defect gene may be asymptomatic and can only be detected when a routine screening FBC is done for any other reasons.

   Inheritance is autosomal recessive. A lethal homozygous state results when an individual inherits genes for both alpha and beta chains from both affected asymptomatic parents.

   Both forms of thalassemia can be classified according to the severity of the disease and transfusion requirement; thalassemia minor, thalassemia intermedia and thalassemia major. The most severe form is hydrop foetalis which the foetus will die in utero or shortly after birth.

   In thalassemia major, the patient will require blood transfusion after one year of life, when foetal haemoglobin is switched to an abnormal adult form.

   For thalassemia intermedia, the patient may require transfusion much later in life and the degree of haemolysis is usually precipitated by infection, pregnancy and surgery. And toward the end, the requirement may be more as the spleen grows larger and sequestrate more blood cells.

   Patients with thalassemia minor can be asymptomatic and lead normal life. But their condition can be worsened by concomitant iron or combined deficiencies, pregnancy, infection or any condition that might accelerate haemolysis.

   Although transfusion can prolong life, especially when combined with iron chelation therapy, females with this disorder historically have been infertile. However, the number of successful pregnancies in these patients has been increasing. These patients require frequent transfusions throughout the pregnancy.

5. Other types of anaemias

   Diamond-Blackfan anemia and sickle cell diseases are rarely found among Malaysian population. However, in the future, we might see more of these conditions as there will be more people from Africa settle in this part of the world.

6. Blood transfusion in pregnancy

   Blood transfusion may become necessary for patients with severe anaemia especially for those who are close to term. The level of haemoglobin at which transfusion is required may be lowered among patient with chronic anaemia than those who develop acute haemolysis. It is difficult to give absolute recommended haemoglobin level at which to transfuse. However, transfusion should be considered in women at or above 34 weeks gestation who have haemoglobin less than 7g/dl. Severe anaemia should be corrected prior to delivery to prepare for the unforeseen antepartum or postpartum haemorrhage.

Recommendation

Pregnant mothers are encouraged to adhere to routine antenatal check-up and follow instructions given. This is important to ensure the wellbeing of mother and child.

References

• Hoffbrand AV et al: 2011. Postgraduate Haematology, 6th Edition