I had an u/s at 6 1/2 weeks and we were able to see and hear the heartbeat...it might depend on the experience level of the one doing the ultrasound and how good the equipment is.
Oh :/ I have a dr appt this tuesday and I am so looking forward to hearing the babys heartbeat! I'll be 7wks 2 days at the time so I hope I get to hear it
I read online today that it is very possible to hear a heartbeat on a doppler as early as 8 weeks but I don't think that most doctors start using dopplers until 10-12 weeks because not every baby's heartbeat can be heard that early.
at 8 weeks you might not hear it, but you could see it. If you don't have an ultrasound until 12 weeks you may not see/hear much till then.
You can start to see it around 5 1/2 - 6 1/2 weeks, then at around 11 weeks you can hear it (If I remember correctly).