Prenatal testing: Is it right for you?
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.
Types of prenatal testing
Prenatal testing includes both screening tests and diagnostic tests:
Oct. 22, 2015
- 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.
See more In-depth
- Ostrer H. Basic principles of genetic counseling for the obstetrical provider. http://www.uptodate.com/home. Accessed July 15, 2015.
- Raby BA, et al. Genetic counseling and testing. http://www.uptodate.com/home. Accessed July 15, 2015.
- American College of Obstetricians and Gynecologists Committee on Ethics. ACOG Committee Opinion No. 363: Patient testing — Ethical issues in selection and counseling. Obstetrics and Gynecology. 2007;109:1021. Reaffirmed 2012.
- Frequently asked questions. Pregnancy FAQ165. Screening tests for birth defects. American College of Obstetricians and Gynecologists. http://www.acog.org/Patients/FAQs/Screening-Tests-for-Birth-Defects. Accessed July 15, 2015.
- 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.
- Allyse M, et al. Cell-free fetal DNA testing for fetal aneuploidy and beyond: Clinical integration challenges in the US context. Human Reproduction. 2012;27:3123.
- Wolfberg A, et al. Noninvasive prenatal testing using cell-free nucleic acids in maternal blood. http://www.uptodate.com/home. Accessed July 15, 2015.