Did anyone test positive for Down syndrome and was the baby born without it?

I had my blood drawn about two weeks ago and it came back positive for Down syndrome. I’m currently 17 weeks. I wanted to know the name of the test but my doctor treated me as if she was in a rush and I tried asking more questions and she simply said it’s 80% accurate. She then said not to worry about it until I have my appointment with the specialist. That’s 3 weeks from now and I feel like its too long to wait without any more answers. Im currently 34 years old and I just had a baby in November 2020 without Down syndrome and no one in my family or my fiancé’s family has Down syndrome so I’m really wondering how accurate this test is.