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:
Aug. 04, 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 noninvasive prenatal testing. 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, 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.
- Noninvasive prenatal testing. If a screening test such as the nuchal translucency or quad screen 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 a noninvasive prenatal test. Noninvasive prenatal testing is a sophisticated blood test that examines fetal DNA in the maternal bloodstream to determine whether your baby is at risk of certain conditions. The testing can also be used to determine a baby's sex and rhesus (Rh) blood type. This type of testing is much more specific than traditional first and second trimester screening. A normal result might eliminate the need for a more invasive prenatal diagnostic test.
- Diagnostic tests. If a screening test or noninvasive prenatal testing 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 a more-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.