Here's the ultrasound showing the strong heartbeat! 169 beats/minute, right in the middle/top of the heart rate range.
Baby Santiago facing forward -- we think you can see the arms if you look closely (We could see the arms and leg "buds" pretty easily during actual ultrasound.)
The doctor was very happy with the growth and we could hear the heartbeat really, really well - nice and strong. It was a pretty amazing moment!