5 weeks is still very early for scan, can barely even see anything other than a super small sac. Dont worry. Diff body diff development rate. Some will only see yolk sac at 6 weeks. But by 8 weeks, should already have a heartbeat.
I saw the yolk sac when I went for the 6 weeks scan (but embryo size was at 5+4 weeks at that point of time)
Anonymous