Hi BW,

I really don't believe it's bypassing natural selection, as the embryologists will be searching for the best-looking, best-moving sperm in the sample. They aren't just going to catch any old sperm, they will be looking for quality.
Yes, that is true. But I assume there is more to quality then can be visually seen through a microscope.

Also - ICSI doesn't guarantee fertilisation. I've had eggs injected that failed to actually fertilise. Don't know whether that's a sperm problem or an egg problem as it happened on cycles where I was hyperstimulated and egg quality was pretty poor. It also happened on the non-hyperstimulated cycle, which is why we went from 12 mature eggs to only 3 that fertilised, even using ICSI.
Yes, it is hard to say which was the problem ... the eggs or the sperm. But it is possible that one reason that some eggs (that are implanted with a sperm via ICSI) fail to fertilise is due to the sperm selected by the technician. The mysterious unexplained fertility problems that some couples experience could be due to some level of quality in either eggs and/or sperm that we are yet to be able to detect. I guess it could also just be chemistry ... maybe some eggs and sperm just do not "combine" correctly. IUI or IVF may help avoid this in some cases???

SD