yeah that is kinda weird.
That really sounds weird that a Dr would not tell them. I would have ask.
well it's actually my cousin's wife. but no the doctor didn't inform them, so they were asking and i just decided to look it up and ask. thanks for helping explain the possibilities, it really helped alot.
In that case, I agree with texasangel. Either one is a bit slower to develop than the other...or only one is viable and the other one is what they call a vanishing twin (where no embryo develops).
One might have implanted later and so it's slow developing or it could be a vanishing twin. Your doctor didn't tell you what that meant? He/She should have informed you.
no two sacs with one yolk.
Do you mean there's only one sac with two yolk sacs inside? If so, it could be identical twins!