Ooh I have a story about heart rates! At my midwife appointment yesterday, she could not get a heartbeat on the doppler despite about 10 minutes of trying. She reassured me that it was likely due to my tipped uterus and in addition to her calmness, I just had a feeling that everything was OK.
The midwife was going to order an ultrasound, but then the senior midwife came into the room to give it a try herself. (I think she privately expressed worries to the senior midwife even though she was projecting calm to me.)
Senior midwife also couldn't find a heartbeat after 5 minutes so said, let me try something a bit different. She rotated my uterus with her hand (getting pretty personal, but it didn't hurt at all) and somehow by internally tilting it forward, was able to get the heartbeat! And it was 150! And then she started crying because she was so relieved for me. So that was all kind of unexpected and cool! Even though I usually freak out at the least bit of potentially bad medical news, in this case I was really calm because I just had that feeling everything was OK.
When I got home I googled it and lots of people with tipped uterus at 13 weeks or so reported similar issues w/doppler.