Was just wondering, Bec, what position were you in when your GP used the doppler? I had a trip to the hospy for monitoring after a GP appt at around 38 weeks because bub's heart rate was dropping considerably between movements. I had some monitoring at the hospital and everything was just fine - a really healthy looking CTG. Turns out that the rate was dropping because I was flat on my back. Each appt after that we listened to bub while I was propped up with a couple of pillows and leaning slightly to my left. No problems.
I am sure that no one will rush you in for a c-sec... You will probably be given a CTG at the hospital and they will advise you from there. All the best, and try not to stress out

ETA: I wonder if it is just an indication that there's less room to move around in there? If bubs is less active then the heart rate will be lower, like Alan said.