Anyone else have 2nd tri blood work come back positive for Downs?

I just had a geneticist call me and tell me that my second trimester blood work came back positive for Downs Syndome, but then she said not to worry that this test gets a lot of false positives, especially for twins and she is not too concerned but she wants me to come in for an ultrasound and amniocentesis.  I'm super worried and scared for my babies.  On one hand I need to know for sure but on the other hand having the amnio also has a risk or miscarry. Anyone else out there got this news?