sac a little smaller than expected - 5wks

Had an early scan yesterday due to a miscarriage in November and the pregnancy was still there but my gyne mentioned the sac being a little smaller than expected.  Can the sac have a growth or is this a bad sign for another miscarriage? As it's still really early, hard to see much / anything other than the sac at this stage - had bloods done and second bloods booked tomorrow but next week feels like a lifetime away to get the results :0(