Continues from previous page
What are the options for the parents if the fetus is affected?
That is entirely up to them and it will depend on the degree of severity of the inherited condition.
As a general statement, both alpha-thalassaemia trait (where individuals are healthy) and HbH disease (where there is chronic anaemia but normal life expectancy) are compatible with continuing the pregnancy. When the diagnosis is that of alpha-thalassaemia major (all four genes missing or affected), the situation is more difficult.
What are the consequences of carrying a pregnancy where the diagnosis for the fetus is alpha-thalassaemia major?
The pregnancy itself is almost invariably associated with complications. The most difficult is pre-eclampsia, which can be exceptionally severe and life-threatening for the mother. If she manages to carry on, delivery is another tricky time. The fetus usually suffers from oedema (hydropsy) and vaginal delivery may be impossible.
A caesarean section, possibly in the presence of severe pre-eclampsia, may in itself endanger the life of the mother. Add to all these, the fact the baby will survive for minutes, at most hours.
This is one prenatal diagnosis that, on paper, should lead to termination of pregnancy. The final decision, of course, rests with the parents.
Will the child of an alpha-thalassaemia trait mother inherit the defective gene?
Not necessarily. Since she contributes two of the four alpha genes (the father contributing the other two), and since she has two or three normal genes herself, she may very well contribute the normal ones; if the father is not affected, this particular child will be unaffected.
As can be seen, there is an element of lottery on whether the child inherits the defective gene or not. The chances of what happens depends on how many defective genes she is carrying as well as whether or not the father is also a carrier.
The pre-pregnancy or pre-test counseling is meant partly to deal with this issue in detail for each particular couple.
Are any special measures required for delivery in alpha-thalassaemia?
Pregnancies for carriers of alpha-thalassaemia are largely routine affairs, even if the baby inherits the defect. The only exception is when the fetus ends up with alpha-thalassaemla major (as discussed above). As such, no special measures are called for during pregnancy, other than folic acid and sometimes oral iron supplements. Likewise, delivery does not call for any special measures.