Alpha-thalassaemia and pregnancy
How does alpha-thalassaemia differ from beta thalassaemia?
In several respects. However, the most important is that in alpha-thalassaemia (α-thalassaemia), the problem is that of missing (rather than defective) genes. Different type of genes are affected (alpha, rather than beta), even though they are also to do with production of another component of the blood pigment haemoglobin.
Is this condition found world-wide?
Yes, but its highest concentration is in South-East Asia and, to a lesser extent, the Indian sub-continent.
Are there different sub-types of alpha-thalassaemia?
Yes, but we shall concentrate on the main types. Suffice it to mention here that alpha-thalassaemia major (where all four alpha genes are missing) is fatal. Affected babies are born very sick and survive for a few hours at most.
What is the carrier situation in alpha-thalassaemia?
There are several sub-groups, which makes this considerably more complex to describe than beta-thalassaemia.
However, the true carriers are those who have one or two missing alpha genes (there are usually four). It is called alpha-thalassaemia trait.
The carriers are clinically healthy and lead normal independent lives. Pregnancy may be the first time their compromised oxygen-carrying capacity is put under strain.
HbH disease and pregnancy
What if the individual has three missing alpha genes out of the four?
These patients tend to have chronic anaemia. This is brought about by constant destruction of the red cells in the body, the so-called haemolytic anaemia. This type of anemia is not exclusive to people with alpha-thalassaemia.
Such patients are said to have HbH disease.
Are any special measures required for pregnancy in individuals with the alpha-thalassaemia trait?
Special measures are seldom required. Their anaemia can be treated with oral iron supplements and folic acid. If severe, blood transfusion is given but not injectable iron.
Are any special measures required for pregnancy in individuals with three missing genes (HbH disease)?
As mentioned before, those patients tend to have haemolytic anaemia as a chronic problem. As such, they do not have iron deficiency, so iron is never required as a supplement. However, folic acid supplements are crucial because they have an exaggerated consumption of this in their bodies.
The minimum supplements should be 5 mg daily.
Is antenatal diagnosis possible with alpha-thalassaemia?
Yes. The fetal status can be established through DNA studies preferably following CVS or placental biopsy near the end of the first trimester (eleven to thirteen weeks).
Genetic screening and counseling of parents is a pre-requisite, to determine the probabilities of the fetus being affected and the extent. Then the parents need to know what they would want to do in each possible eventuality.