Same deal here, BG. Rip snorter embies, and no luck. If they were iffy or highly fragmented etc, I'd understand, but you sort of assume if you have a number of good'uns it should happen. We had this discussion with our FS recently, and she said it's totally normal, and that perfectly good embies aren't a free ride to pregnancy, and it's nothing to do with the ability of the mother to accept the embryo. In 100 years they'll probably know the factors why, but for now we have to play the numbers game.