Twins - only one heartbeat at 7 weeks

Hi all,

I had a successful ivf transfer last month and I am 7 weeks today.. I had some bleeding at 6 weeks and had a scan which showed one sac with a faint heartbeat.. told to rescan at 7 weeks.

Today we have been told there are two sacs! One measuring 6 weeks 6 days with a strong heartbeat and the second measuring 5 weeks 2 days and empty.

Iv been told to scan again in a week.

I’m not very hopeful as I know vanishing twin syndrome is more common in ivf pregnancy’s but I think I can see a yolk sac on the scan.

Did anybody have similar experience and see a heartbeat at a later date?