Q&A: My AFP test came back with a risk of Downs syndrome, but I don't understand what it means.

Before you get too worried about your unborn baby's health, keep in mind that the AFP is a "screening" test to assess your risk. A positive AFP doesn't mean you'll definitely have a child with Down syndrome. Based on your results, your risk of having a baby with Down syndrome is one in 149, or more than twice the risk for your age group. But 1:149 is still a long shot.
Since your chances exceed your age group's risk, you may want to take additional steps to see if your unborn baby does indeed have Down syndrome. First, you can consult with a perinatologist, who specializes in high-risk pregnancies. Next, you may also consider (and your doctor may recommend) what's called a level-three ultrasound. The perinatologist will perform this ultrasound and look at physical clues that may indicate whether your unborn baby has Down syndrome. One of these indications is a thickening at the base of the neck. Again, the results of the ultrasound aren't conclusive.
Based on the ultrasound, your doctor may recommend an amniocentesis or chronic villus sampling (CVS) for confirmation. Both of these tests will give you accurate results but they carry a risk of miscarriage. None of these tests (even the AFP) are mandatory, but they will give you a better idea about your baby's risk of having certain genetic disorders, like Down syndrome.
Soon, you'll probably have an option of taking a simple blood test early in your pregnancy to determine positively whether your baby has Down syndrome (eliminating the need for the amniocentesis). Researchers developed a test in 2008, but it will take time before it's widely available.