As far as I was aware there are varying degrees and it can progress quickly or slowly or not at all....
The growth scan could be cautionary.. IUGR can be caused by PET so they may just want check that everything is as it should be
I *think* they can give medication if its mild-moderate but they will do more tests to confirm (ie bloods and normally a 24 hour urine test too)...
Hugs, if it is PET hopefully its mild and you can just carry on as you are with just a bit of extra monitoring!