Heyside- I think this is true, however I also think it's different where you are going PGD. For PGD your embryos have to be hatching to be able to be biopsied and that doesn't always happen on day 5. As an example mine was an expanded blast on morning of day 5 but not hatching so they had to let it go to day 6. Who knows it may have hatched later in the day but they only check them once a day as I understand multiple checks in a day aren't good for them. Mine was hatching on morning of day 6 and so was biopsed and it has led to a pregnancy. Many people have day 5 expanded blasts transferred and get pregnant and if they aren't doing PGD they don't need to worry about the hatching status. I wonder how they factor in grading e.g if you had an AA day6 versus a BB day 5 would they still select the day 5 over the day 6? I dont know. For what it's worth my FS said they were "almost" seeing equal success rates with day 5's and day 6s but I don't know if he was talking about equal grade day 5s and 6's.