Many genetic disorders happen when someone has two bad (faulty) copies of a gene, one from each parent. In such cases, if one has only one faulty copy, they won’t have symptoms of the genetic condition, but are a "carrier” for it. The baby will be born with the disorder only if both parents are carriers and both pass the bad gene to him.
If both parents are carriers for a certain genetic disorder, the chance that they will both pass over the faulty genes to their baby will be 25 per cent.
To test if the couple is a carrier of a genetic disease, the doctor usually takes a small sample of their saliva or blood during a checkup before they plan to get pregnant or before marriage, if they plan to do so.
These tests can also be done during pregnancy to determine status of the baby, but getting tested before pregnancy gives everyone a greater range of options and more time to make decisions.
If the test results of one partner are positive for a faulty gene, they may be required to undergo further specific tests which involve more comprehensive and elaborate testing.
Although these tests may seem too overwhelming for the couple, they ensure that everything will be fine with their baby and might prevent future frustration to the family due to a baby born with debilitating inherited disorder.
Genetic testing for these conditions will depend on the availability of the testing facilities, as well as the medical expertise.
In Rwanda and Africa at large, or people of African ancestry, one of the tested commonest bothersome inherited disorders is sickle cell disease which causes a blood disorder that leads to anaemia, a weakened immune system, and other life threatening health complications of the affected child.
Another genetic disorder called beta thalassemia is also more common to people of African and Mediterranean descent and this can also be screened for during couple genetic testing. This condition may lead to bone abnormalities, liver problems, and anaemia in a baby. In some cases, a baby with this disorder may not even survive.
Other disorders screened for which aren’t so common in Africa include cystic fibrosis (common in Caucasians, a life-threatening condition that causes lung damage and digestive problems), Tay-Sachs Disease (disorder of the central nervous system which is usually fatal in early childhood) and Fragile X Syndrome (developmental problems, including learning disabilities and mental retardation, is not linked to a specific ethnic background).
Though there are many other recessive genetic diseases, they are not routinely checked for because they’re either very, very rare or because the right tests have not been developed yet.
If during this genetic couple testing both partners are found to be positive for carrier screening before they get a baby, they have several options. They might choose to become pregnant and have prenatal diagnostic tests to see if the foetus has the disorder, and can decide the next course of action after thorough education and counselling by their gynaecologist and geneticist. They can also choose to use in vitro fertilisation (IVF) with donor eggs or sperm to become pregnant. With this option, the embryo can be tested before it is transferred to the mother’s uterus.
After thorough discussion with their doctor and many considerations, the couple might also choose either not to become pregnant together or get married to each other at all.
It is important to know that if this carrier screening is done after one has already become pregnant, the options are more limited. In either case, a genetic counsellor, gynaecologist, or other health care professional, can explain the risks of having a child with that disorder.
At Rwanda Military Hospital, this genetic couple testing, education and counselling is done by a skilled geneticist. Couples are, however, advised to come a few months before they plan to have a child as some of the results of this screening might take some time to process.
Dr Ian Shyaka , Resident in Plastic surgery, Rwanda Military Hospital,
iangashugi@gmail.com