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Birth defects tests are done during pregnancy to look for possible problems with the baby (fetus). Birth defects develop when something is wrong with genes or chromosomes, an organ, or body chemistry. A birth defect may have only a mild impact on a child's life, or it can have a major effect on quality of life or life span.
Birth defects include:
There are two types of birth defects tests: screening and diagnostic.
Screening tests for birth defects are blood tests and ultrasounds. The blood tests are used to look for the amount of certain substances in your blood. The doctor uses an ultrasound to look for certain changes in the baby. Diagnostic tests involve taking some of the baby's cells to look at the genes and chromosomes.
No test is 100% accurate. A test may be negative even when the baby has a birth defect. This is called a false-negative test result. It's also possible that a test will be positive—meaning the test result is abnormal—but the baby does not have the problem. This is called a false-positive test result.
You may have only first-trimester tests or only second-trimester tests. Or you may have an integrated test. This test combines the results of tests you have in your first trimester and second trimesters.
Pregnant women and their partners can choose whether to have a test for birth defects. For example, you may want to have tests to know if there is a problem so you can work with a doctor and hospital to care for your baby after birth. Or you may want to have tests because you wouldn't want to continue the pregnancy if there is a serious problem. Some women might decide not to have these tests because they would continue the pregnancy regardless of the results.
Talk to your doctor about tests that are available where you live and which tests might be best for you.
If you choose to have a test, you also may want to talk with a genetic counselor. The counselor can talk with you about the reasons to have or not have the test. He or she can also help you find other resources for support and decision-making.
Deciding about testing can be a hard and emotional choice. You need to think about what the results of a test would mean to you and how they might affect your choices about your pregnancy.
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You and your doctor can choose from several tests. What you choose depends on your wishes, where you are in your pregnancy, your family health history, and what tests are available in your area. You may have no tests, one test, or several tests.
Screening tests show the chance that a baby has a certain birth defect. Diagnostic tests show if a baby has a certain birth defect.
When they are usually done
First-trimester screening (first part of integrated screening)
10 to 13 weeks
Nuchal translucency (usually done as part of the first-trimester screening)
11 to 14 weeks
Cell-free fetal DNA (an option for women at higher risk)
10 weeks or later
Triple or quad screening (second part of integrated screening)
15 to 20 weeks
Ultrasound (pictures of baby's body)
18 to 20 weeks
Chorionic villus sampling (CVS)
The nuchal translucency test and the first-trimester blood tests are often done together in what is called the first-trimester screening.
First-trimester tests also can be done as part of an integrated screening test. This test combines the results of the first-trimester tests (first-trimester blood tests and nuchal translucency test) with those of a second-trimester test (the triple or quad screening).
Cell-free fetal DNA
The cell-free fetal DNA test looks at fetal DNA in a pregnant woman's blood. It can help find genetic problems like Down syndrome or trisomy 18. This test is an option for women who have risk factors for having a baby with certain birth defects. It's not used as a general screening test or for women who are carrying twins.
The decision to have a test for birth defects is personal. You have to think about your age, your chance of passing on a family disease, your need to know about any problems, and what you might do after you have the test results. Your spiritual beliefs and other values also may play a role in your decision.
Some birth defects—such as a cleft lip or cleft palate or certain heart problems—can be fixed with surgery after birth and sometimes even with surgery during pregnancy. Some other defects cannot be fixed.
You may decide to have the tests because:
You may decide not to have birth defects tests because:
Other Works Consulted
Wapner RJ, et al. (2009). Prenatal diagnosis of congenital disorders. In RK Creasy et al., eds., Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice, 6th ed., pp. 221–274. Philadelphia: Saunders Elsevier.
Current as of: May 29, 2019
Author: Healthwise StaffMedical Review: Sarah Marshall MD - Family MedicineAdam Husney MD - Family MedicineKathleen Romito MD - Family MedicineElizabeth T. Russo MD - Internal MedicineSiobhan M. Dolan MD, MPH - Reproductive Genetics
Current as of:
May 29, 2019
Medical Review:Sarah Marshall MD - Family Medicine & Adam Husney MD - Family Medicine & Kathleen Romito MD - Family Medicine & Elizabeth T. Russo MD - Internal Medicine & Siobhan M. Dolan MD, MPH - Reproductive Genetics
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