Noninvasive prenatal testing is much more sensitive and specific than traditional first and second trimester screening. As a result, noninvasive testing can often help women who have certain risk factors avoid invasive testing, such as:
- Amniocentesis. During this procedure, a small sample of the fluid that surrounds and protects the baby during pregnancy (amniotic fluid) is removed from the uterus for testing.
- Chorionic villus sampling (CVS). During CVS, a small sample of the wispy projections that are part of the developing placenta (chorionic villi) are removed from the placenta for testing.
Amniocentesis and CVS both carry a slight risk of miscarriage.
Your health care provider might recommend noninvasive prenatal testing first if:
- You have risk factors for having a baby who has a chromosomal condition. Noninvasive prenatal testing can determine whether your baby is at risk of a chromosomal condition. Risk factors might include older maternal age or having previously given birth to a baby who has Down syndrome, trisomy 13 or trisomy 18. Your health care provider also might recommend noninvasive prenatal testing if you've gotten worrisome results from another prenatal screening test.
- You're a carrier of an X-linked recessive disorder. X-linked recessive disorders, such as Duchenne's muscular dystrophy or a blood-clotting disorder (hemophilia), typically affect only males. Noninvasive prenatal testing can determine the sex of your baby earlier than an ultrasound. While noninvasive prenatal testing can determine your baby's sex, it won't determine if your baby has the disorder. Depending on your test results, a genetic counselor can help you understand the next steps.
- You have an Rh negative blood type. Noninvasive prenatal testing can determine your baby's Rh factor. If you're Rh negative and your baby is Rh positive, you might produce Rh antibodies after exposure to your baby's red blood cells. This is called becoming sensitized. (This is typically not a concern during a first pregnancy, but can be a concern during subsequent pregnancies.)
While noninvasive prenatal testing is currently recommended for women at high risk of carrying a baby who has a chromosomal abnormality, research is under way to see how it might be helpful for other women. Research is also being done to see what other chromosomal abnormalities and genetic conditions can be detected through this type of testing.
Feb. 23, 2013
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