A Test for Down Syndrome

A new screening test for Down syndrome that can be done earlier and that is more reliable than the triple-screen blood test is available for expectant mothers soon. The test, called the combined first-trimester screen, is done at 10 to 13 weeks. It includes an ultrasound to measure the thickness of skin (called nuchal translucency) on the back of the fetus's neck. The thicker the area, the greater the likelihood that the baby has Down syndrome.

According to a three-year study of 38,000 women, this ultrasound, coupled with two blood measurements and calculated with a woman's age, is 85 percent effective at detecting a Down's baby -- and unlike blood tests alone, has a low rate of false positive results. Women who are deemed high risk due to screening go on to get an amniocentesis, which can give a definitive answer as to whether or not a baby has Down syndrome.

Originally published in American Baby magazine, April 2004.