I had this in my first pregnancy (as well as 1:5 risk of T13, T18, T21, due to really high HCG). I had an amino to investigate and that luckily came back clear.
Throughout the pregnancy I had 4 weekly growth scans, which then became 2 weekly as there was slow growth, these then became weekly scans, checking cord flow and liquor, with growth scan 2 weekly as well.
The consultant had already said that he would be wanting to induce me before 40weeks due to restricted growth, however I ended up being induced at 37 weeks due to pre-eclampsia. Low PAAP A increases your risk of pre-eclampsia, although no one ever told me this until afterwards!
My baby was born healthy but small (4lb6) and after a few days on transitional care was deemed well enough for discharge. However, I wasn't so we didn't leave until a week after the birth - the doctors weren't sure what caused my health issues though, as they weren't the ones that are normally associated with pre-eclampsia.
Baby was back in and out of hospital with failure to thrive and some other health issues, but these weren't linked to the low PAAP A so I won't bore you with the details. Baby is now a 'normal' healthy 2 year old and I'm pregnant with my second - hormone levels and growth are all normal at this stage, but I'm having extra scans to keep a close eye on everything.
Good luck with your pregnancy and try not to worry.