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Why it's done
By Mayo Clinic staffFirst trimester screening is done to evaluate your risk of carrying a baby who has Down syndrome. The test also provides information about the risk of Edwards syndrome.
Down syndrome causes lifelong impairments in mental and social development, as well as various physical concerns. Edwards syndrome causes more severe delays and is often fatal by age 1.
First trimester screening doesn't evaluate the risk of neural tube defects, such as spina bifida.
Because first trimester screening can be done earlier than most other prenatal screening tests, you'll have the results early in your pregnancy. This will give you more time to make decisions about further diagnostic tests, medical treatment and the course of the pregnancy. If your baby is diagnosed with Down syndrome, you'll also have more time to prepare for the possibility of caring for a child who has special needs.
Other screening tests can be done later in pregnancy.
An example is the quad screen, a blood test that's typically done between weeks 15 and 20 of pregnancy. The quad screen can evaluate your risk of carrying a baby who has Down syndrome or Edwards syndrome, as well as neural tube defects, such as spina bifida.
Some health care providers choose to combine the results of first trimester screening with the quad screen — although you won't learn the final results until both tests are completed and analyzed.
Remember, first trimester screening is optional. Test results only indicate whether you have an increased risk of carrying a baby who has Down syndrome or Edwards syndrome, not whether your baby actually has one of these conditions.
Before the screening, think about what the results will mean to you. Consider whether the screening will be worth any anxiety it might cause, or whether you'll handle your pregnancy differently depending on the results.
You might also consider what level of risk would be enough for you to choose a more invasive follow-up test.
- Canick JA, et al. First trimester and integrated screening for Down syndrome and trisomy 18. http://www.uptodate.com/index. Accessed Aug. 27, 2012.
- Benacerraf BR. Sonographic findings associated with aneuploidy. http://www.uptodate.com/index. Accessed Aug. 27, 2012.
- Canick JA, et al. Second trimester maternal serum screening for Down syndrome. http://www.uptodate.com/index. Accessed Aug. 27, 2012.
- Routine tests in pregnancy. American College of Obstetricians and Gynecologists. http://www.acog.org/~/media/For%20Patients/faq133.pdf?dmc=1&ts=20120827T1517335564. Accessed Aug. 27, 2012.
- Messerlian GM, et al. Overview of prenatal screening and diagnosis of Down syndrome. http://www.uptodate.com/index. Accessed Aug. 27, 2012.
- Ostermaier KK. Management of Down syndrome. http://www.uptodate.com/index. Accessed Aug. 27, 2012.
- Harms RW (expert opinion). Mayo Clinic, Rochester, Minn. Sept. 11, 2012.
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