Small gestational sac

Hi everyone,
I have a question in reverse regarding a thread title I saw a bit further down on this forum... (the title is "large gestational sac"
I'm currently 12 weeks pregnant and have my dating scan next Tuesday. The ultrasound at 11 weeks (more scans due to recurrent miscarriage) went well. So, heartbeat was good, baby's size was right on track (even a few days ahead), but the gynecologist mentioned that the gestational sac was quite small... nothing else was said about it. They said it would be checked again at the next scan at 12 weeks. Does anyone have an idea if this could be harmful? I don't feel completely reassured...
The midwife listened to the heartbeat yesterday, and thankfully it was fine...
Has anyone had experience with a small gestational sac around 12 weeks? And how did things go for you?
Mamsie