Health 101: Genetic Testing Before & During Pregnancy

What are some of the most common genetic diseases?

• Cystic fibrosis is a life-threatening condition that causes lung damage and digestive problems. About 30,000 people in the U.S. have the disease, which mostly affects Caucasians of Northern European descent. Organizations like the National Institutes of Health, the American College of Obstetricians and Gynecologists, and the American College of Medical Genetics have recommended nationwide genetic testing for CF for all adults since 2002. According to a recent study in the New England Journal of Medicine, the number of babies born with cystic fibrosis in Massachusetts dropped by about 50 percent in the four years after this recommendation was made and testing came into wider use compared to the four years before.
• Sickle cell disease, most common in people of African and Mediterranean backgrounds, causes a blood disorder that leads to anemia, a weakened immune system, and other health complications.
• Thalassemia is another blood disorder common to people of African and Mediterranean descent. It typically causes anemia and bone growth and liver problems; in severe cases, some babies born with the condition may not survive.
• Tay-Sachs Disease, which mainly affects people of French Canadian and Eastern European Jewish descent, is a disorder of the central nervous system that's usually fatal in early childhood. Eastern European Jews also face an increased risk for another nervous system disorder called Canavan disease as well as a number of other conditions including familial dysautonomia, familial hyperinsulinism, and Gaucher disease. Your doctor can screen for all of these conditions at the same time.
• Fragile X Syndrome, a condition that can cause developmental problems, including learning disabilities and mental retardation, is not linked to a specific ethnic background. Reviewing your family's health history with a doctor or genetic counselor may help you decide whether you should be screened for Fragile X.

What does genetic testing tell you?

Genetic testing results give you an idea of your risk for passing along genes that can trigger certain diseases in your baby.

• If neither you nor your partner is a carrier, your baby will not inherit the condition.
• If you are a carrier, but your partner is not (or vice-versa), your baby will not inherit the condition.
• If you and your partner are both carriers, your child has a 25 percent chance of inheriting the condition.

While genetic testing can give you and your partner visibility into your health history and your chances for a healthy pregnancy and baby, it's not totally foolproof. "Some genetic tests, like cystic fibrosis, can only identify some of the mutations in the genes that cause the condition," says Trepanier. So even if you get negative results, there's still a slim chance you could be carriers and pass on the condition to your baby.

Your doctor may be able to recommend a genetic counselor, or you can find one through the National Society of Genetic Counselors (nsgc.org) or the American Board of Genetic Counseling (abgc.net).

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