Genetic testing has led to major medical breakthroughs in the treatment of numerous hereditary conditions. Genetic carrier screening is a type of genetic testing often carried out on prospective parents, sometimes pre-pregnancy, to see whether they carry a genetic mutation which could cause an inherited disorder in their child. In many countries, genetic carrier screening is carried out as a matter of course; pregnant women are often tested for hereditary disorders such as cystic fibrosis, thalassemia, sickle cell disease, and Tay-Sachs disease.
However, there are as many as 100 different diseases that can be detected through carrier screening. Though many of these disorders are rare, a recent scientific survey revealed that 24% of patients screened were carriers of at least one genetic mutation. The same study revealed that the risk of a child being born with a genetic mutation is actually higher than that of having a child with a neural tube defect or Down syndrome.
Genetic Carrier Screening for Prospective Parents
Carrier tests are conducted to see whether a prospective parent might be a carrier of a genetic condition. Carriers often have no symptoms or associated health problems themselves, but there may be implications for their children. Screening is particularly advisable where there is a family history of a particular genetic condition. In addition, members of certain ethnic groups may face an increased risk of developing specific genetic conditions. Genetic screening can be particularly helpful before a couple begins trying to conceive.
How do I go about getting tested?
Usually, the woman is tested first—sometimes simply because women are more likely to be visiting their doctor and undergoing other tests when trying to conceive. If no faulty gene is detected, the father probably will not need to be tested; most disorders are recessive, meaning that they require the faulty gene in both parents. Carrier screening is usually carried out on a sample of the patient’s blood. The sample is taken at the hospital or in the doctor’s office, then sent away to a laboratory for analysis. Certain parts of the DNA chain are examined for genetic mutations linked to specific genetic conditions. Some genetic carrier tests can be done by means of a saliva test, but in the case of Tay-Sachs disease, for example, a blood sample is necessary in order to conduct a special enzyme test.
How long does it take to get a carrier screening result?
The length of time it takes for the result to come through can depend on which genetic condition is being tested for. The amount of time it takes can vary. For example, the results for a cystic fibrosis test could be available within a week or two, whereas some tests could take longer. This is because some genes are harder to analyze than others. In addition, the data produced by the test can take a lot of time and care to check through thoroughly. It’s important that these test procedures are not rushed in order to give the most accurate result possible.
What do the results of genetic carrier screening mean?
A positive carrier screening result means that the laboratory detected a mutated gene, protein, or chromosome connected with a genetic condition. Because members of the same family can have genetic material in common, a positive screening result might also have implications for blood relatives of the patient, e.g. siblings, not just the patient and their prospective children.
If I’m a carrier of a genetic disorder, can I still have healthy children?
The answer to this common question is an absolute yes. As mentioned above, most genetic diseases are recessive disorders, meaning both parents would each need to pass along a faulty gene for any risk of the child developing the condition. Remember that while nearly one in four of us carries one sort of faulty gene or another, some genetic illnesses are incredibly rare—the odds of both parents carrying that same gene mutation are small. Even in a situation where both partners test positive as carriers for the same mutation, the chance that your child will inherit the associated disorder is still only 25%.
What choices do we have if my partner and I carry the same genetic disorder?
It is here that the potential of having genetic screening carried out before trying to conceive really comes to the fore. If you have been screened before getting pregnant, there are several options open to you.
You may decide to continue trying to conceive naturally and have diagnostic tests once you are pregnant to see whether the fetus carries the disorder in question. This type of testing is carried out on cells, either from the fetus or the placenta. These cells are obtained either through amniocentesis or chorionic villus sampling.
You may choose to conceive via in vitro fertilization using a donor’s eggs or sperm, or you could decide to use your own. The benefit of IVF is that the embryo can be tested for genetic condition prior to implantation.
It’s important to remember that there is no one “right” response to the results of a genetic carrier screening. Each couple must decide what is best for their situation and the family they wish to start. A good physician will be able to help you in this process by taking the time to discuss your results with you, explain what they mean, and answer all your questions.