While most babies are born healthy and without birth defects, approximately 3-5% of all babies are born with a birth defect. Some of these babies will have birth defects that are due to or associated with genetic disorders or syndromes. Women are routinely offered a variety of genetic screening tests during their first three months of pregnancy to evaluate the risk for genetic disorders in their unborn baby.
The first trimester screening tests are usually done between the 10th and 13th week of pregnancy. These tests involve measuring the level of certain substances in the mother's blood and obtaining an ultrasound.
Information from these screening tests, along with other risk factors such as a woman's age, a couple's ethnic background, and family history of genetic disorders are used to help calculate the odds that a fetus might be born with genetic disorders such as Down syndrome, cystic fibrosis, Tay-Sachs disease, or sickle cell anemia.
A key fact to remember is that these tests do not diagnose the disorders, but instead, they only screen for the substances and show if there is an increased risk of a disorder. Further testing is always suggested to make a diagnosis.
Abnormal screening test results don't mean your baby is affected. In fact, most of the time, the fetus is not affected with a disorder, even if the screening result is abnormal. Out of 1,000 serum screening tests, an average of 50 will suggest an increased risk for open neural tube defects, but only one or two of the fetuses will have such a defect. Likewise, an average of 40 out of 1,000 will test positive for increased risk of Down syndrome, but only one or two fetuses will actually have the condition.
Whether or not a woman decides to undergo genetic screening is her own choice, as positive results could produce anxiety and conflicting emotions. It's important to understand one's options and to be informed in order to make educated decisions about what is best for you and your family.
If you are pregnant or are planning on conceiving, talk to any of our doctors at your next appointment about any concerns you may have. You can also ask about what screenings or tests are right for you.