Low heart rate

I have yet to post anything on here since I'm more of a watcher and reader... However Friday my husband and I went to see our OB where our little one was measuring 2 weeks behind (unsure of exact ovulation) so no biggie there but the heart rate was measuring 80bpm and the Yolk sac measured larger at 6.5mm. Just curious if anyone has gone through this and had a positive out come or anything similar. Thank you ladies! We return tomorrow morning for hopefully good news!