Prenatal screening and diagnostic tests provide information about whether a fetus has certain genetic conditions or birth abnormalities and are offered to all women during pregnancy. But these tests are optional, so when making your decision, it’s important to understand what prenatal testing can tell you and what it can’t.

Types of Prenatal Testing

Prenatal screening tests can tell you the chances your fetus may have certain genetic disorders or birth abnormalities, such as sickle cell disease, Down syndrome, spina bifida, cystic fibrosis, Tay-Sachs disease and others. Prenatal diagnostic tests can tell you if it actually does.

There are a variety of prenatal screening tests:

·         Carrier screening: This is a blood test parents can undergo prior to or during pregnancy to determine if they are carriers of genes that cause conditions like cystic fibrosis or sickle cell. If both parents are carriers, there is a higher risk of the fetus having a severe form of the disease.

·         Chromosomal screening: The mother’s blood is tested to analyze the small amounts of fetal DNA present and the various protein levels to determine if there are missing or extra chromosomes in the fetus. This can tell you about the likelihood of conditions such as Down syndrome or Turner’s syndrome.

·         Screening for physical abnormalities: Ultrasound and blood tests can be used to help determine the risk of conditions like abnormal fetal heart formation, birth defects, neural tube defects (like spina bifida and anencephaly), and issues with the development of the brain, skeleton, kidneys, abdomen, face and limbs.

Based on the risk level suggested by screening tests, your provider may recommend prenatal diagnostic testing to provide more definitive information. Diagnostic testing is also a consideration if you have a personal or family history of genetic conditions, are over age 35 or have a history of miscarriages or stillbirths.

The two most common forms of diagnostic tests are amniocentesis, in which a needle is used to extract amniotic fluid from the amniotic sac surrounding the fetus, and chorionic villus sampling (CVS), in which a needle is used to remove cell samples from the placenta, either through your abdomen or vagina.

Key Considerations

Some level of anxiety is typical during pregnancy, so it can be helpful to consider what you will do with the test results once you have them. You may decide to proceed with screening tests for the reassurance a result within the standard range can provide, but you should be prepared if that is not the case.

Based on your medical history and personal beliefs, it’s up to you whether or not to have prenatal testing and which types. Some things to keep in mind:

·         Prenatal screening tests only measure risk, and there is always a chance the results are wrong. In addition, diagnostic testing can’t always determine the severity of some conditions. Talk to your provider about the accuracy rates for tests you are considering.

·         There is no medical risk with prenatal screening tests; however, diagnostic tests carry a slight risk of infection, bleeding and miscarriage.

·         Different tests can only be performed at certain stages of pregnancy, so there may be a delay between the results of a screening test and the time when you can have a diagnostic test, if you choose. The results from some tests are available in days, while others take several weeks.

·         Diagnostic testing can provide information that will impact your care and choices during pregnancy. It can also help you and your care team prepare for your baby’s treatment and care after birth.

Your women’s health provider can offer information and resources to help guide your decisions, including a referral to a genetic counselor specially trained in the nuances of genetic testing and results.

Our providers pride themselves on giving compassionate, knowledgeable and non-judgmental care. If you have questions or concerns about your pregnancy, bring them with you to your next prenatal visit or call us to schedule an appointment.

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