Big hugs Stellas Mum...
This is a scary time and I do understand...
Your PAPP-A is low - and yes it's an indicator. Just like a temperature is an indicator to pneumonia - but you could just get a cold... KWIM???
The ratio between the PappA and HCG is not too bad.
To put it into perspective. My PAPP-A was 3 times yours and my baby was born at 28 weeks with a shot placenta... It is just an indicator. In the absence of any other indicator the likelihood is good that your baby is healthy.
I wish I could give you a hug in person. I feel your pain - please let us know when your CVS comes thru.
My thoughts and prayers are with you...