I don't have to, but it's an optional screening for your fetus' CHANCE of having Down's syndrome, Trisomy 18, and neural tube defects such as spina bifida ... Anyone can be at risk, but as you get older the risk is greater ... I have chosen not to have the screening as I will love my child no matter what the case, and in the chance that you are at high risk, amniocentesis and/or cvs needs to be performed for diagnostics, which give you a small but real chance of m/c ... Plus, I know myself if I got high risk results it would just put more stress on me through the pregnancy, and I'm already diagnosed with major anxiety that I am medicated for ... Does that answer your question?