Genetic Screening

Genetic testing during pregnancy can give parents important information about their baby—specifically, whether their child is likely to have specific genetic disorders like Down syndrome, sickle cell disease or cystic fibrosis.

There are two basic types of genetic tests: Screening tests can identify increased risks of chromosomal disorders and a few other things, while diagnostic tests can actually tell you for sure if your baby has a particular disorder.

Genetic screening tests

You and your partner may choose to have carrier screening to find out if you carry the genes for certain inherited disorders and, thus, your likelihood of having a baby with a given disorder. This only needs to be done once, rather than with each pregnancy, because the results don’t change. Prenatal screening tests that use the mother’s blood, along with ultrasound exams, can screen your baby for chromosomal disorders, neural tube defects, and certain defects with the heart, abdomen and face.

Genetic diagnostic tests

In order to know for sure if your baby is affected by certain genetic disorders, diagnostic testing would be needed. These may be either invasive or noninvasive.

Invasive genetic tests include:

• Amniocentesis: A needle is used to take a sample of amniotic fluid, which provides the baby’s DNA for testing. There’s a slight chance of miscarriage associated with this procedure.
• Chorionic villus sampling (CVS): A tissue sample is take from the placenta, which provides the baby’s DNA for testing. The risk of miscarriage is slightly higher than that from amniocentesis, but the test can be done earlier—as early as 10 weeks into the pregnancy.

Noninvasive (or cell-free) DNA testing can also be done using the mother’s blood. This isn’t quite as accurate as the invasive methods, but is less risky for the baby.

Talk to your doctor about whether genetic screening or diagnostic tests are right for you and your pregnancy.

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