I have a bad 3rd stage history too. I Haemmoraged very seriously after my first birth requiring LOTS of blood, don't remember how much now, as well as a years worth of iron injections and three months of terrible fatigue. I haemmoraged fairly badly after my DD's birth, requiring three blood transfusions (I think) and some terrible fatigue as well as depression (I attribute to blood loss and fatigue as well as having a non sleeping baby!) and a bit of blood loss with DS requiring one transfusion. I am still on ferrous grad C (iron tablets) and have a borderline iron count.
I tried to have a natural 3rd stage with DS but it was not to be. I ended up losing too much blood and the placenta was taking too long to come out, so I agreed to have the synto. It came out not too long afterwards. I ended up having to have one transfusion anyway cause I lost too much blood. I also fainted when I got into the shower several hours after having bubs. I had a completely natural 1st and 2nd stage though, so was more than happy with that (not to mention mega proud of myself!).
Good luck making your decision, and with your birth!!