though I'd bump this ... Lots of mums here have had bubs from day 2-3 transfers when cells are bewteen 4-8 cells or more and a few from day 5 (Blastocysts)

AT Westmead Fertility centre in NOV 2005 I asked for my embryos to be blastocysts (it wasn't any extra) but I think the to 'qualify' is to do more with how many fertilised eggs you get.

As they rather you had an embryo to transfer than none.As going to Blasts you need more than 6 at some clinics as it tends to leave you with only 1 -3 embryos or less.There is a higher rate of embryos succumbing. Some don't freeze well either.

The embryos are just younger IYKWIM - everything else is the same.