I'm not sure what tests they had done on her, but a lady that I go to church with said that she was told that her unborn daughter HAD Trisomy 18. She still planned on having her baby and guess what...she is perfect, no trisomy 18 and she is around 12 years old. These tests aren't always fool-proof.
I had a positive AFP test (showing increased risk for spina-bifida). Needless to say, I was a nervous wreck over that possibility. My doctor sent me to a specialist and I had a repeat Level 2 u/s. Then they had me repeat it 2 weeks later to be sure. Everything checked out fine and my son was born with NO problems.
Hang in there (I know easier said than done) and if it will help you feel better about it, have them send you for a repeat u/s. I'll keep you and the baby in my prayers.