Heartbeat?

Went to my OBGYN for my 8 week scan I found out my due date and I saw the baby's heartbeat but she refused to do use the device on the ultrasound cart to hear a heartbeat she said she didn't want to to harm the baby I'm not really sure why . this early in the pregnancy the baby can't hear anything I thought. I'm very confused if someone could give me some advice or someone has been through this that would be awesome this early in the pregnancy the baby can't hear anything I thought. What are your thoughts??