If my embryos were frozen on day 5, and then thawed for an embryo transfer, are they considered day 5 or day 6? they were graded 4ab and 4bb. thanks!

Day 5: If they were frozen on d5, then thawed and transferred without spending additi90nal time in media they are considered d5. You should always consult your ivf doctor for specifics, since he/she knows your case better than we do. Embryos are sometimes graded 1, 2, 3..., sometimes a, b, c, but sounds like you have a great bunch...Best of luck!