Twins but only hear 1 heartbeat

Annalee

I had <a href="https://glowing.com/glow-fertility-program">IVF</a>, we put back 2 embryos and on my 5 weeks scan we saw 2 sacs with yolk in it, we came back at 6 weeks U/S to hear heartbeat but we only hear 1 heartbeat and the doctor can still see yolk sac but cant see fetal pole or any heartbeat, he said the position of the embryo is deeper so he can't see it or it develop slow than the other one as they are not identical twins, ask us to come back next week to make sure.

What do you think guys? Please if someone who has same situation, i need your stories.

I am hoping the other embryo catch up.