Our doctor called on Monday to let me know what happened with the three embryos that they kept culturing for us even though they weren't keepers. These were the three 4CFs. Basically one of them did nothing, one made it to six cells, and one made it all the way to a very ugly looking morula, or as our doctor put it "dark and grainy". I forget exactly how she phrased it, but from what she said it was pretty clear that it wasn't going to make it to blastocyst. Actually, having one of these guys make it to a morula was a bit surprising.
Obviously conclusions to be drawn from this are rather limitted. Since 4CF is a fairly normal quality for my embryos it is encouraging to know that such embryos can keep dividing. On the other hand, it looks like the clinic was not being entirely arbitrary to select against these embryos. It also makes me feel better to have cultured them, I would not have wanted to just discard anything that had a fighting chance.
I was surprised at how positive everyone was about our decision to culture the embryos. I think the reason that this isn't routinely done is that for most couples it would raise false expectiations. We made it clear that we understood that these embryos were not of high enough quality to be frozen, and that we just wanted data. I am really glad that they did this for us. It's not clear-cut data, but it is still information that I value.