Even though my wife is only 26 years old, the results from her prenatal tests show that she has a high risk for having a baby with Down syndrome. According to the AFP tests, her probability is 1:280. We'd like to try further testing to figure out if our unborn baby has Down syndrome, but the doctor has told us that the tests available carry potential risks for pregnant women. My wife already had her 20 week ultrasound, are there any other tests she can take to give us some peace of mind?
Prenatal testing can be unnerving. I'm glad that you understand that the prenatal test you describe—the AFP, or alpha-fetoprotein test, usually given between the 15th and 20th week of pregnancy—is a risk assessment test, it's not a "yes" or "no" sort of result.
The next least invasive test would be a Nuchal Translucency (NT) where combined with a high-resolution ultrasound and blood tests, your health care provider will be able to get a better idea of your risk of having a child with Down syndrome. But like the AFP, this is a risk assessment test, meaning its not definite. Also, this particular test is not available in all areas of the country.
The next round of testing would be either a Chorionic Villus Sampling (CVS) or an Amniocentesis. Both tests carry the risk of miscarriage and both are considered invasive. With the amnio, a technician will insert a needle into your abdomen and then into the amniotic sac to collect a sampling of amniotic fluid. From that sample, the technician will then be able to determine with 98-99% accuracy whether your unborn baby has Down syndrome. An amnio, carries with it a risk of miscarriage. According to the American Pregnancy Association (APA), with this particular procedure, "the risk of miscarriage ranges from 1 in 400 to 1 in 200."
With the CVS procedure a needle is either guided through your abdomen or inserted through the cervix to collect chorionic villi cell samples from the placenta. As with an amnio, the procedure is not without risks, 1 out of every 100 procedures result in miscarriage, states the APA. The CVS is equal in its accuracy to the amnio. One advantage is that a CVS can be performed earlier in the pregnancy than an amnio.
You will need to weigh these concerns with your wife—whether the risk of miscarriage is acceptable in order to have definitive results about your unborn baby's well-being.
In the future, testing for Down syndrome will most likely be much easier. A new, simple blood test that picks up the unborn baby's DNA in the mother's blood can give parents accurate results and without the risk of miscarriage. Right now, the test is not available to patients. But it should be available soon.