Our donor ended up producing fourteen eggs. Since we are doing a split cycle (where the clinic is keeping half), we get seven. That seems like a very low number to me, and now I'm second-guessing my decision to do the split cycle. Our donor had averaged 22 eggs in the past, so I was hoping for more. My coordinator says, "Seven is a good number, and I expect you'll have something to transfer," but the idea that we might not is making my stomach churn right now.
Statistically, we can expect about five of the eggs to be fertilized. That's a very rough guess. Then it's a matter of how many will develop well. I've read that about half make it to the blastocyst stage, which is what we're aiming for. All we need are two good ones to give us the 70% chance that we're hoping for. Anything more can be frozen for another try, but my coordinator warned me not to expect to have enough to freeze when doing a split cycle, so I won't be disappointed if that happens. I just want my two embryos.
I did find out more about the embryo grading. Actually, when they are embryos, the only thing measured is the number of cells. On Day 3, they hope to have embryos with six or more cells - this is considered good development. When they are at the blastocyst stage at Day 5, there is structure beyond the cells, and the cells have differentiated into, I think, at least two types. There is then some kind of grading system, but it is not universal - it differs from clinic to clinic - and I won't find out exactly how mine works until the time comes. (I suppose I could demand to know now, but I don't think it would be productive.)
We'll find out tomorrow morning how many were fertilized.
Now the stress and uncertainty begins in earnest.