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.
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. It 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.
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.
Health Tools help you make wise health decisions or take action to improve your health.
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.
First-trimester screening (first part of integrated screening)
Nuchal translucency (usually done as part of the first trimester screening)
Triple or quad screening (second part of integrated screening)
Ultrasound (pictures of baby's body)
Chorionic villus sampling (CVS)
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 with those of a second trimester test (the triple or quad screening).
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
You may decide not to
have birth defects tests because:
For more help on deciding about tests, see the topics:
NCBDDD aims to find the cause of and prevent birth
defects and developmental disabilities. This agency works to help people of all
ages with disabilities live to the fullest. The website has information on
many topics, including genetics, autism, ADHD, fetal alcohol spectrum
disorders, diabetes and pregnancy, blood disorders, and hearing loss.
The Genetics Home Reference provides information on hundreds of genetic conditions. The website has many tools for learning about human genetics and the way genetic changes can cause
disease. It also has links to additional resources for people who
have genetic conditions and for their families.
The March of Dimes tries to improve the health of babies
by preventing birth defects, premature birth, and early death. March of Dimes
supports research, community services, education, and advocacy to save babies'
lives. The organization's website has information on premature birth, birth
defects, birth defects testing, pregnancy, and prenatal care.
Other Works ConsultedAmerican College of Obstetricians and Gynecologists (2007, reaffirmed 2009). Invasive prenatal testing for aneuploidy. ACOG Practice Bulletin No. 88. Obstetrics and Gynecology, 110(6): 1459–1467.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.
April 4, 2012
Sarah Marshall, MD - Family Medicine & Siobhan M. Dolan, MD, MPH - Reproductive Genetics
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