Low Papp-a levels

Marisol

My NT scan at 12 W 6D said my baby’s neck was measuring at 2.8 Dr said when it’s 3 that’s when they get concerned. Asked if I wanted to get the NIPT done to check for Downs, trisomy 13 & 18. Test results came back negative for all three but other test shows low papp-a. Anyone else have this situation?