Tay, we didn't get heart rates at the 13 week scan, but at our 10 week, twin one (top) was 171bpm. Twin two was 164bpm!
Thanks Biscuits! Most so far, seem to be convinced bottom is girl. Funnily enough, I said the same in the ultrasound room, that if one was a girl it would be twin two! I certainly will be updating you all when we know in a few weeks time!