Prenatal Screening Tests
Pregnant women get lots of routine prenatal tests including blood tests, blood sugar tests (also called glucose monitoring), and ultrasounds.
Screening tests are different. They're optional, low-risk tests that don't diagnose anything. Instead, they give you a sense of your baby's chance of having certain conditions. While helpful in many cases, these tests can produce a lot of false positives. That means the test says your baby has a problem when she or he really doesn’t. This can cause a lot of unnecessary stress.
While screening tests are recommended for all women, whether you get them is up to you. Your doctor or midwife may suggest you speak with a genetic counselor before you make any decisions. If you have any questions or concerns, be sure to bring them up before having any tests.
Screening tests include:
Nuchal translucency screening. During your first trimester, your doctor or midwife may do a special type of ultrasound to check the thickness of your baby's neck along with blood tests to look for certain things that may be linked to birth defects. The combined results can tell if your baby has a higher risk of having Down syndrome, trisomy 18, and other chromosome disorders.
Quad marker screen. During the second trimester, your doctor or midwife can do this blood test. It helps show your baby's risk of Down syndrome or other chromosome problems and neural tube defects, such as spina bifida and anencephaly.
If your tests come back normal, you may decide to stop there and trust that your baby doesn't have a neural tube defect or genetic disorder. Remember, a bad result doesn't mean your baby has a birth defect. It means your baby may have a higher risk. You may want to follow up with further testing to learn more.
Women over age 35 may skip screening tests and go directly to prenatal diagnostic testing.
Prenatal Diagnostic Tests
If results from screening tests raise concerns, or if you want further reassurance that your baby does not have certain problems, your doctor or midwife may suggest these diagnostic tests. Unlike screening tests, these tests are accurate ways of diagnosing problems. However, they do have some risks, including a slightly higher rate of miscarriage. You need to weigh the pros and cons.