What are the chances of miscarriage again?

sunyDi
I had an ultrasound last week which dated baby to be 7 weeks exact with a heartbeat , im now 8 weeks and have to go next week at 9 weeks. What are the chances baby will have no heartbeat? My last pregnancy baby never had a hearbeat . Im just paranoid im scared me and hubby are happy well he's mostly happy im constantly worried .