Embryos are graded once they have divided. Do you grade fertilised eggs?
Embryo grading is based on the size and shape of the cells within them, as well as the amount of fragmentation of cells seen within the embryo. When your eggs are fertilised (day one), they will not have cleaved (divided) and are, therefore, only a single cell. This means that we do not assign these embryos a grade until the following day (day two) by which time they should have cleaved.