Twins or one baby and a yolk sac?!

Ciara

Went to have what I thought was my 8 week ultrasound today and turns out I am measuring at 6 weeks 4 days. We heard a heartbeat in one but couldn’t pick up one in the other. Doctor wasn’t sure if we were seeing a sac or another baby. Follow up ultrasound next week. Someone please tell me it’s a yolk sac 😭 I am terrified.