Why culture to the blastocyst stage (Day 5)?
If we have a good number of good quality embryos on Day 3 (should be at least four embryos at the 8 cell stage), we can gain more information about the embryos by culturing them for 2 more days without risking the possibility of not having any blastocysts available for replacement. We do not expect all embryos to reach the blastocyst stage, so it is a way of refining our selection of the best quality embryo(s) for your replacement.
