Down Syndrome - Exams and Tests
Testing before becoming pregnant
You may want to consider genetic testing for Down syndrome if you are planning to become pregnant and you have a family history of the condition. Genetic testing can confirm whether you or your partner carry the translocation chromosome, which increases your risk for having a child with the translocation type of Down syndrome. But this kind of testing does not detect whether your child is more likely to have the trisomy 21 type, which accounts for most Down syndrome cases.
Genetic counseling can help you understand why genetic testing is done, what the results mean, and how the results may affect you and your family.
Screening during pregnancy
Screening does not diagnose Down syndrome but rather provides information about the likelihood that your fetus will have the condition. Screening tests include:
- Fetal ultrasound and blood tests in the first trimester (combined screening). One advantage of combined screening is that it can be done earlier in your pregnancy than some other tests. An ultrasound image can show a greater-than-normal amount of fluid at the back of a fetus's neck. The skin fold thickness measurement estimates the distance between the surface of the skin and the neck bones (nuchal fold). The skin fold test may not be widely available, because only a specially trained provider can do it. A blood test checks the mother's levels of human chorionic gonadotropin (hCG) and pregnancy-associated plasma protein-A (PAPP-A).
- Integrated screening. This screening involves both first and second trimester tests to predict the risk of having a child with Down syndrome. This test may not be available everywhere. It is one of the most accurate tests. 5 The results are reported only after both sets of tests are finished. This can be cause for concern for women who would like to know test results early on.
- Maternal serum triple or quadruple screen test. These are second trimester tests. The triple test (triple screen) checks the
amounts of the following 3 substances in your blood:
- Alpha-fetoprotein (AFP)
- Human chorionic gonadotropin (hCG)
- Estriol (uE3)
The test is called a quadruple screen (quad screen) when a test for inhibin A is added. Inhibin A is a protein that is produced by the fetus and the placenta.
Screening tests for Down syndrome and other conditions require your consent. Some women find that knowing their chances of having a child with Down syndrome helps them to prepare for the possibility. Others are more comfortable going through their pregnancy without having this information.
The type of screening tests given, alone or in combination, depends on your goals and preferences. For example, when a mother is most concerned with screening accuracy and does not want to have amniocentesis, her doctor may recommend a combination of fetal ultrasound and blood test during the first trimester plus a triple or quad screen during the second trimester.
Diagnosis during pregnancy
WebMD Medical Reference from Healthwise
Down Syndrome Topics
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