Genetic testing is when a blood test is given to prospective or expecting parents to look for abnormal genes that can lead to certain diseases in their baby. Most genetic diseases are known as "recessive disorders," which means that each parent needs to pass along an affected gene to the baby in order for the child to be affected. In other words, if you screen positive for a genetic abnormality but your partner does not, your child will not inherit the condition. And even if you both screen positive, there's only a 25 percent chance your baby will have the disease.
You can get a carrier screening at your ob-gyn's office with a single blood test; you typically receive the results in two weeks. Most often, a woman is tested first (only because you're more likely to see your doctor regularly if you're in trying-to-conceive mode) and if those results don't show a problem gene, her partner usually doesn't need to be tested.
Genetic testing is ideally done before you start trying to get pregnant, says Angela Trepanier, MS, CGC, co-director of the genetic counseling program at Wayne State University and president of the National Society of Genetic Counselors. "But because so many pregnancies are unplanned, many couples get screened early in pregnancy," she says.
Getting screened before you try to get pregnant can give you reassurance (if you or your partner is not a carrier, it's one less thing to worry about when do you get pregnant) or can help you make an informed game plan for pregnancy. If it turns out that you are both carriers, you can be prepared for and bone up on what it means to have a baby with the genetic condition, choose to learn about certain prenatal tests to check whether your baby's healthy, or you can consider other options like egg or sperm donation or adoption.
Getting tested once you become pregnant (if you hadn't done so ahead of time) can help you and your doctor decide the right prenatal tests for your baby, and what to look for if you choose to have them. If you know that your baby's at an increased risk for having cystic fibrosis or sickle cell disease, for instance, your doctor can look for those conditions specifically through either a CVS (chorionic villi sampling) or amniocentesis.
Your ethnic background and family history are the main factors that determine whether or not genetic testing is right for you. "That's because the diseases for which genetic testing is currently offered tend to be more common among certain ethnic groups," says Trepanier. Here's an example of groups who are more likely to have certain genetic diseases.
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, says Trepanier.
Genetic testing results give you an idea of your risk for passing along genes that can trigger certain diseases in your baby.
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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