Cell free fetal DNA testing stories

Hey ladies.
We opted to have this screening done at 12 weeks due to my age. All ultrasounds have been perfect. There are no abnormalities to be found. We also have no family history of genetic disorders on either side. 
The results came in that the baby is a girl - and that she's showing positive for Trisomy 18. Needless to say, we are shocked and devastated. They want to do an amnio to be sure of the results. So, that will happen next week. 
My question to the universe is this:  has this happened to you?  We are being told that the cell free DNA test is 99% accurate. That's a terrifying number in our case. 
Just trying to find some hope to grasp to here since we can see that physically she's showing no signs of this. (No clinched fists, she has a nasal bone, the thickness behind her neck is normal, her feet are normal, heart is normal, heartbeat is normal....)