Hi tennisgurl,
I think it just completely depends on the embryos. Some of them are just not meant to be, and if that's the case it's better to know sooner than later. But with 5 fertilized I wouldn't worry too much about not having some to transfer on day 3. Your odds are pretty good that you'll have some & remember, it just takes one! It's definitely quality over quantity as far as embryos are concerned. Just concentrate now on getting yourself to a healthy & calm place for the transfer day.
Best of luck to you,
2ndtimer
I just finished my first IVF, they retrieved 5 eggs, injected 4, but only one actually fertilized (started dividing, growing...). So I only had one to transfer, but it only takes one, I'm proof to that. We did a 5dt since we only had one. I'm not sure how they determine if they will do a 3dt or a 5dt, but at my clinic there is some sort of deciding factor because they do both ??? I think it has something to do with the number and quality of the embryos.