ultrasound, no visible heartbeat

Jai
A friend of mine is suppose to be around 7 and a half weeks pregnant (from her last period), she had her ultrasound done and the baby is measuring 6 weeks 4 days, they could see the sack and the baby but couldn't find a heart beat. Thoughts? I'm not sure what to say to her other than don't stress yet. They've told her to go back in two weeks for a follow up scan.