When donated eggs are used, 50-60% of the embryos should make it to the blastocyst stage with majority be of top quality. Based on your post, this donor did not measure up in terms of quality (quanity was O.K.). There are a few explanations. (1) Life is like a box of chocolates... Athough a first time donor may look good on paper, E2 levels and U/S, the quality of the eggs cannot be ascertained until the eggs are fertilized and the embryos cultured to the blastocyst stage. We have also seen this kind of substandard development in our donor program (see footnote). (2) Poor quality sperm (i.e. excessive DNA fragmentation) can negatively affect embryo development to the blastocyst stage and the quality of the resulting blastocysts. If there was a contributing male factor, this may the reason. (3) The stimulation was mismanaged - unlikely, but possible. (4) Substandard lab conditions - again, unlikely with a DE rate of 67%, but possible in your specific case.
Your chances are significantly dimished from 67%. The other problem with low grade blastocysts is that are more likely to cause "chemical" and "empty sac" pregnancies. There are not enough stem cells in the low grade blastocysts to continue development.
Footnote: In our program, we can identify with the recipient's disappointment when only poor quality embryos are available for transfer in a DE cycle. In our minds, once you have accepted using DE (and that always a difficult decision) you are depending on us to give you the best chances of success by adequately screening the donor to minimize this kind of situation. So, it is our policy to guarantee at least two good quality blastocyst stage embryos for transfer in a DE cycle. If we find ourselves in the same situation as you (and it does happen occasionally because you just never know on a first time donor), we perform another DE cycle for free. This reduces the stress experienced by the recipient couple. As far as I know, we are the only program that does this. www.northhudsonivf.com