Thalassaemia – Can IVF prevent it?

What is thalassaemia?

Thalassaemia is a genetic blood disorder which is caused by an abnormal gene. A person with thalassaemia is unable to produce normal, functioning haemoglobin, a protein in red blood cells responsible for oxygen transportation in the blood. When the body is not able to produce normal, functioning haemoglobin, the affected person suffers from anaemia.

Thalassaemia is passed on from parent to child and can affect both males and females. In Singapore, about 4.5% of the population are carriers of the thalassaemia gene (thalassaemia minor). Carriers of the thalassaemia gene are people with one affected gene. They are generally healthy and can lead a normal life. Most of them do not know that they have it. However, this abnormal gene can be passed on to their children.

Thalassaemia major is a severe form of anaemia. When a person has inherited two thalassaemia genes, one from each parent, he or she will suffer from severe anaemia, which leads to poor growth and development as well as a shorter life expectancy. The affected person will need blood transfusion every month to sustain life. At present, a bone marrow transplant is the only hope of possible cure for thalassaemia major.

When one of the parents is a thalassaemia minor, there is a 50% chance that their children will be normal and 50% chance that they will inherit one of the affected gene and become a carrier of the thalassaemia gene (thalassaemia minor). None of their children are at risk of becoming a thalassaemia major.

When both parents are thalassaemia minor, there will be 25% chance that their children are at risk of inheriting both thalassaemia genes and becoming a thalassaemia major. There is also a 50% chance that their children will inherit one of the affected gene and become a carrier of the thalassaemia gene (thalassaemia minor). Only 25% chance that their children are normal.

When one of the parents is a thalassaemia major, all of their children will inherit one of the affected gene and become a carrier of the thalassaemia gene (thalassaemia minor). None of their children are at risk of being a thalassaemia major.

When one parent is a thalassaemia major and the other parent is a thalassaemia minor, there will be 50% chance that their children are at risk of inheriting both thalassaemia genes and becoming a thalassaemia major. There is also a 50% chance that their children will inherit one of the affected gene and become a carrier of the thalassaemia gene (thalassaemia minor).

How can I prevent this genetic disease from passing down to my children?

Couples who are at risk of having thalassaemia major offspring can undergo preimplantation genetic testing (PGT) to ensure that the affected thalassemia genes will not be inherited. The primary intent of PGT is to allow selection against embryos that have inherited single gene variants that lead to serious genetic conditions, so as to improve their chances of having a healthy child. In order to perform PGT on embryos, carrier couples must undergo IVF.