I had considered doing a natural third stage but my
OB recommended against it. He said there is a higher chance of haemorrhaging if you opt for a physiological approach and he has witnessed it on several occassions. That was enough for me to think twice about it.
I did a bit of research and often it's fine to deliver the placenta without any drugs but I figured it really isn't going to hurt me to have the shot and get the placenta out sooner rather than later. After all that hard work I think I'll be quite happy to finish off the labour and get on with just bonding with my baby.
That's just my personal opinion though.