Twins or no twins?

Ann

What do you think? The ultrasound was done at 6 weeks 2 days. There was only 1 heartbeat as of the last ultrasound. The baby on the bottom had a heartbeat. But there is something visible on the top left as well.The lady who did the ultrasound wasn't sure what it is. She thought it could be a blood vessel or another yolk. What do you think? Any similar experiences?