Well, I can't remember my exact grading, but I can tell you that we put two embryos back in - an excellent 5 day blastocyst, and a much slower 5 day morula. And, even with a low grade on the second one, they still both stuck. I ended up losing one (not sure which one) and one is my healthy baby girl. So I do know that people get pregnant with lower graded embies all the time. Obviously the lower the grade, the lower the chances, but it seems that it still happens around here!
2010 - my IVF/PGD baby girl born on September 2! Thank you Dr. Lin!