7 week ultrasound

I have my first ultrasound scheduled for 7 weeks 2 days. For those of you who have had an ultrasound at 7 weeks were you able to hear the heart beat? I had a miscarriage back in May at 12 weeks & am nervous I might not hear anything/see anything at 7 weeks. I'm just trying to decide if I want to push back my apointment to 8 weeks or if everything should be fine at 7 weeks! Any advice?