Abnormal nuchal fold at 19 weeks

Adrienne
Hi all,
I had my autonomy scan today. We were told after the scan that our little guy has a thickened nuchal fold (5.4 mm). We are a bit freaked out since our 12 week Down syndrome testing came back within normal range (2.1 mm). Thus, I wanted to see if anyone else has had this happen or is currently going through the same thing. 
This will be our 3rd baby but first boy! It's so hard to feel excited when we have this little cloud over us.