Down syndrome

Alisha
At my first trimester screening my results were 1:5100 chance of downs. Just got the results of my 20 week ultrasound & turns out baby has a marker for downs. I have to go for more tests at a specialized radiology office.
My question is has anyone had a normal first screening & then markers appear later & everything be fine??? My husband is freaking out. Any experience would be helpful. TIA