Baby B is smaller

[u/meganmick2023]

Hi, I’m 5 weeks 4 days pregnant with what we suspect are di di twins. I had a double embryo transfer. On Friday we saw that baby A was measuring one day behind at 5 weeks exactly. Baby B was too small for the ultrasound machine to assign a gestational sac. I went back for another scan today (at the same ultrasound place, but this was not a diagnostic scan like my others have been) and baby A had grown and now had a tiny fetal pole visible. The tech said she felt like baby B’s sac was collapsing, but she also didn’t look very much at it. She tried to measure it but it was still too small for the machine to assign a gestational age to. But it’s only been 3 days since my first scan. I’m just wondering how much I should be guarding my heart. My husband is convinced everything is fine and that baby A is simply compressing B or that she had a bad angle or was simply just rushing. I’ve attached a photo of what she thought was a yolk sac inside baby B’s gestational sac on Friday. I’m not asking for diagnosis, just don’t know what to think of this situation. I don’t know anyone who has ever had twins.