7 w 1 day. Twins???

Mari

Just had an ultrasound today. They gave me this picture and said they see something else that looks like a second yolk sack but not another baby. Anyone ever had this happen? In the pic the baby is in between the arrow things, the first yolk sack is underneath and the second possible yolk sack is on top. Anyone have anything similar to this? They said they don't think it is twins but what could that be?