At 8 weeks pregnant, it should be much higher. I did lose my last pregnancy with a hr of 76 at 7 weeks. But, that does not mean you will miscarry. I've seen plenty of stories on here of low heart rates and successful pregnancies. Keep your chin up. Try not to worry. I know it's hard. I've been there. I'm 12 weeks pregnant now and 2 weeks away from having lost my baby a year ago. It has been very difficult to push my worry away. Sending positive vibes your way.