Who Gets the Test?
The first trimester screening is a safe, optional test for all pregnant women. It's a way of checking your babies' risks of certain birth defects, such as Down syndrome, Edward's syndrome (trisomy 18), trisomy 13 and many other chromosomal abnormalities as well as heart problems.
Women with twins may be less likely to get the full first trimester screening. The results aren't as accurate as they are in women pregnant with single babies.
What the Test Does
The screening involves two steps. A blood test checks for levels of two substances -- pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin. A special ultrasound, called a nuchal translucency screening, measures your babies' nasal bones as well as the fluid at the back of their necks. A high volume of fluid can be a sign of problems.
The combined result of the blood tests and the ultrasound gives you some sense of your babies' risks. However, it's not a diagnosis. Most women who have an abnormal screening go on to have perfectly healthy babies.
Whether you get this test is your choice. Some women want the test so they can prepare. Others don't. They may decide that knowing the results wouldn't change anything. Or they feel that the test could result in unnecessary stress and invasive testing. However, knowing of possible risks would allow for increase monitoring during your pregnancy as well as giving you delivery options (special hospital, pediatric surgeon availability).
How the Test Is Done
The first trimester screen won't harm you or your babies. A technician will take a quick blood sample from your arm or fingertip. The nuchal translucency screening is a normal ultrasound. You'll lie on your back while a technician holds a probe against your belly. It will take between 20 to 40 minutes.
What to Know About Test Results
You should have the results in a few days. If your results are normal, your babies have a low risk of these birth defects. If they're abnormal, your doctor may suggest further tests to rule out problems. These could include ultrasounds or invasive procedures, like CVS or amniocentesis.
Try not to worry if your results are abnormal. Remember: this test can't diagnose birth defects. It only shows if your babies have a greater risk than average.
The ultrasound part of this test -- the nuchal translucency -- is as accurate with twins as it is with single babies. However, the blood test results are less accurate.
Sometimes your test results are combined with a second trimester screening. In that case, you may not get test results until your second trimester. Or you may get the results, and then get combined results after the second test.
How Often the Test Is Done During Your Pregnancy
You would get the first trimester screen once between the 11th and 13th week.
Other Names for This Test
Nuchal test, integrated screening
Tests Similar to This One
Triple screen, quad screen, MSAFP, sequential screening