Carrier Screening
For patients who are considering pregnancy, it is important to determine if they are at risk of passing any genetic diseases on to their children. Genes are what controls an individual’s physical makeup. Half of a child’s genes come from the mother/egg and the other half comes from the father/sperm. Genes are stored on chromosomes, and all cells in the body have 46 chromosomes. Therefore, a child inherits 23 chromosomes from the egg and 23 chromosomes from the sperm. There can be defects in genes and/or chromosomes that are inherited by a baby. Sometimes, these defects are “silent”, meaning that the parents are not aware that they were carriers for any defects or mutations. Thus, it is recommended for patients to undergo what is called “carrier screening” prior to attempting pregnancy. This can identify defects that may place offspring at a higher risk of inheriting a genetic disorder.
Cystic fibrosis is a good example of this. Cystic fibrosis (C.F.) is a genetic (inherited) disease that severely affects breathing and digestion. About 30,000 children and adults in the U.S. have this disorder, with approximately 1 in 30 Americans being a carrier for cystic fibrosis (although the chance of being a carrier varies among individuals of different ethnic backgrounds). Individuals who are carriers for C.F. do not have any symptoms and are often unaware that they are carriers because they only have a mutation in one of their genes. However, if two individuals who are C.F. carriers have a child, this child has a 25% risk of having the cystic disease illness. In other words, the only way to inherit C.F. is if both parents are carriers for a C.F. gene mutation. Luckily, this is fairly rare. The point of testing individuals is to determine what couples are at risk of having a child for C.F. so that appropriate counseling and measures can be taken.
We test for a number of other inherited disorders at our office. What testing is recommended for each couple varies depending on ethnic background and underlying risk. Testing involves the collection of a blood or saliva sample from both partners. Some of the other disorders that we test for at our office include, but are not limited to:
- Spinal Muscular Atrophy (SMA)
- Fragile X disorder
- Tay-Sachs disease
- Sickle cell disease
- Alpha and Beta Thalessemia
- Canavan Disease
- Familial Dysautonomia
If we identify that you and/or your partner are a carrier for a specific disorder, we will review the results with you and arrange for you to see a genetic counselor who can discuss the results with you in detail and answer any additional questions that you might have. A genetic counselor is someone who is trained in medical genetics and counseling. He or she can help you determine if you want further testing and, if so, which testing is appropriate.
