Dectecing down syndrome?

amnio helps dectec down syndrome. How? A doctor or technician uses ultrasound to pinpoint a pocket of amniotic fluid a safe distance from both the baby and the placenta. Then, under continuous ultrasound guidance, the doctor inserts a long, thin, hollow needle through your abdominal and uterine walls to extract a small amount of amniotic fluid. You may feel some cramping, pinching, or pressure during the procedure. Ok so I have a question, how safe is it and all the mommies tht have done it was it worth it?