Prenatal testing, including screening and diagnostic tests, can provide valuable information about your baby's health. Understand the risks and benefits.
By Mayo Clinic Staff
Pregnancy is a time of great anticipation — and, sometimes, anxiety.
You might worry that your baby will have health problems. While most babies are born healthy, it's important to understand your options for obtaining details about your baby's health.
Prenatal testing includes both screening tests and diagnostic tests:
- Screening tests. Prenatal screening tests can identify whether your baby is more or less likely to have certain birth defects, many of which are inherited disorders. These tests include blood tests, a specific type of ultrasound and prenatal cell-free DNA screening. Prenatal screening tests are usually offered during the first or second trimester. Screening tests can't make a definitive diagnosis. If you get a positive result your health care provider will discuss your options for a diagnostic test to confirm the diagnosis.
- First trimester screening tests. During your first trimester, your health care provider will offer a blood test and an ultrasound to measure the size of the clear space in the tissue at the back of a baby's neck (nuchal translucency). In Down syndrome and in certain other conditions, the nuchal translucency measurement is abnormally large.
- Second trimester screening tests. During the second trimester, your health care provider will offer an additional blood test called the quad screen. This test measures levels of four substances in your blood. Results indicate your risk of carrying a baby who has certain chromosomal conditions, such as Down syndrome. The test can also help detect neural tube defects — serious abnormalities of the brain or spinal cord.
- Prenatal cell-free DNA screening. This sophisticated blood test examines fetal DNA in the maternal bloodstream to screen for the increased chance for specific chromosome problems, such as Down syndrome. This screening might be considered if your age, family history or medical history suggests an increased chance for having a baby with certain chromosomal abnormalities. It also might be considered if another screening test, such as the nuchal translucency or quad screen, indicates a possible problem. This screening can also provide information about a baby's sex and rhesus (Rh) blood type.
- Diagnostic tests. If a screening test or prenatal cell-free DNA screening indicates a possible problem — or your age, family history or medical history puts you at increased risk of having a baby with a genetic problem — you might consider an invasive prenatal diagnostic test. A diagnostic test is the only way to be sure of a diagnosis. Some diagnostic tests, such as chorionic villus sampling — in which a sample is taken from the placenta — or amniocentesis — in which a sample of amniotic fluid is removed from the uterus — carry a slight risk of miscarriage.
Prenatal screening tests for fetal abnormalities are optional. It's important to make an informed decision about prenatal testing, especially if you're screening for fetal conditions that can't be treated. Before going forward, consider these questions:
- What will you do with the test results? Normal results can ease your anxiety. However, if prenatal testing indicates that your baby might have a birth defect, you could be faced with wrenching decisions — such as whether to continue the pregnancy. On the other hand, you might welcome the opportunity to plan for your baby's care in advance.
- Will the information shape your prenatal care? Some prenatal tests detect problems that can be treated during pregnancy. In other cases, prenatal testing alerts your health care provider to a condition that requires immediate treatment after birth.
- How accurate are the results? Prenatal screening isn't perfect. The rate of inaccurate results, known as false-negative or false-positive results, varies from test to test.
- What are the risks? Weigh the risks of specific prenatal tests — such as anxiety, pain or possible miscarriage — against the value of knowing the results.
- What is the expense? Insurance coverage for prenatal testing varies. If the test you're considering isn't covered by your insurance plan, are you willing and able to cover the cost of the test on your own?
Prenatal testing can provide information that influences your prenatal care. Remember, though, some screening tests introduce the need for careful personal decisions. Ultimately, the decision to pursue prenatal testing is up to you.
If you're concerned about prenatal testing, discuss the risks and benefits with your health care provider. You might also meet with a genetic counselor for a more thorough evaluation.
A genetic counselor can help you understand:
- The chances that your baby might be affected by a certain condition
- How the condition would impact your baby's life, including your baby's physical and mental development and quality of life
- Possible treatment options, either during pregnancy or after birth
Taking the time to evaluate your options will help you make the best decision for you and your baby.
Oct. 22, 2015
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- Frequently asked questions. Pregnancy FAQ164. Diagnostic tests for birth defects. American College of Obstetricians and Gynecologists. http://www.acog.org/Patients/FAQs/Diagnostic-Tests-for-Birth-Defects. Accessed July 15, 2015.
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