Hi Rainbow (yes I am still here lurking from time to time!)
I also have an increased risk for pre eclampsia. I was told after my first trimester screening that the blood result for my PAPP-A level was low - which can in some cases be indicative of poor placental function later on in pregnancy - but is usually fine in most cases. Poor placental function can cause pre eclampsia. Im sure they were talking about your PAPP-A levels.
I am birthing at a birth centre and this has not caused me to not be allowed to birth there so Im sure you will be fine. The docs just wanted me to have a 36 week scan to assess growth, placental function and AFI - which I had yesterday - and everything is totally normal! placental working perfectly - baby is a bit of a fatty! (which is totally strange because I am only 55kg!) So as soon as 37 weeks rolls around which is next week I am starting operation get into labour! Have already started my raspberry leaf tablets and evening primrose oil but will see chiropractor next week. And then lots of walking, might even try s*x (oh god)!
Anyway, I have researched heaps on PAPP-A if you want anymore info.