Has this happeed to anyone else?

Last week i went to the doctor and they tested me to see if the baby would have any birth defects. Well this morning they called and said some of the blood came back positive so now they have to send me to a specialist to see if there really is something wrong. She said they have had plenty of womens blood test positive for this and when they go to the specialst nothing is wrong. I mean me or the father has no history of any abnormalities in our family. Has this happened to anyone else?.