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Common Questions About Genetic Carrier Testing

If you’re thinking about starting a family, there is a lot to consider. Budgets, baby names, and nursery design are just a few of the things to start thinking about.  Depending on your family’s health history, you might also want to participate in genetic carrier testing. This simple, accurate procedure can help provide key insights on your pregnancy and the health of your unborn child.

What Is A Genetic Carrier?

In order for a child to inherit a genetic disorder, it must receive two genes for that disorder. A carrier is an individual either a mother or father who has one gene for a particular disorder. Carriers usually don’t have a genetic disorder themselves nor do they exhibit any obvious signs or symptoms.

Who Should Be Tested For Genetic Carrier Status?

Any woman who’s already pregnant or thinking about becoming pregnant can benefit from genetic carrier testing. As a general rule, doctors and OB/GYNs recommend women undergo carrier screening for cystic fibrosis, hemoglobinopathies, and spinal muscular atrophy. 

It is possible to undergo carrier screening for other disorders as well. For example, targeted carrier screening works to detect disorders based on ethnicity and family history, while expanded carrier screening uses a blood sample to test for dozens of different disorders. 

How Are Genetic Diseases Passed Through Generations?

Genes contain a coded outline that determines a person’s genetic traits. They are arranged in 23 pairs of chromosomes, with half of each pair coming from each parent. Genetic diseases are passed on in one of three ways:

  • Autosomal dominant inheritance. Autosomal dominant inheritance occurs when a child receives a normal gene from one parent and an abnormal gene from the other. In families where one parent carries a defective gene, a child has a 50% chance of inheriting a specific disorder. However, the severity of the disorder varies from person to person.
  • Autosomal recessive inheritance. Autosomal recessive inheritance occurs when both parents carry a faulty gene. Even though the parents are carriers, they usually don’t exhibit any symptoms of a particular disorder. In families where both parents carry a defective gene, children have a 25% chance of inheriting both copies of the gene and in turn, the disorder. They also have a 50% chance of inheriting one gene and becoming a carrier themselves. 
  • X-linked recessive inheritance. X-linked, also known as sex-linked recessive inheritence, occurs when a mother carries a defective gene on one of her X chromosomes. In families where a mother carries a defective gene, sons have a 50% chance of inheriting a specific disorder. Daughters also have a 50% chance of inheriting a disorder, but they usually aren’t affected because they receive two X chromosomes one from their father and one from their motherb this typically offsets any negative effects from the mother’s faulty gene.

Are Men Or Women More Likely To Be Carriers of Genetic Disease?

Men and women are both carriers of genetic disease. For example, about 1 in 259 women carry Fragile X syndrome and could pass it onto their offspring. At the same time, about 1 in 800 men carry Fragile X. This means their daughters will also be carriers. 

It’s common for general practitioners and OB/GYNs to recommend carrier testing to the partner most likely to be a carrier first. If test results show this person isn’t a carrier, no further testing is necessary. However, if test results show your partner is a carrier, you’ll want to undergo testing too. 

Once you receive the results of your genetic carrier screening, your OB/GYN or general practitioner can refer you to a genetic counselor who can help you interpret the results. This can help you better plan for the future and help provide peace of mind.

Sources:

https://www.acog.org/Patients/FAQs/Carrier-Screening?IsMobileSet=false#is

https://www.mda.org/disease/how-are-genetic-diseases-inherited

https://www.integratedgenetics.com/patients/pre-pregnancy/inheritest

https://www.whattoexpect.com/getting-pregnant/health-and-wellness/carrier-genetic-screenings/#who

https://www.fraxa.org/fragile-x-syndrome/cause/

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