I am 6w3d along and had my first ultrasound today. Doc detected a heartbeat but said it was slow. The baby measured at 5w6d. I've been reading around and seems lower heart rate might result in miscarriage. I miscarried a few months ago and a heart beat was never detected (this is my second pregnancy), so of course, I am scared. Anyone experience a slow rate around 6 weeks and then had a healthy pregnancy?