Chronic Villus Sampling (CVS)

Has anybody had this test done? I had a free cell DNA test and it came up 70% possibility for trisomy 18 and the doctor is recommending a CVS test. I am only 12 weeks pregnant with my first baby and I am sad and very scared and worried the test might harm my baby. I am also going crazy not knowing what is going on. Today we had a more detailed ultrasound and everything looks perfect but the doctor said that no abnormal markers show up so early in an ultrasound. Had anybody had a high probably of a trisomy and had a normal baby?