I've figured out during my time doing IVF that statistics and averages mean bugger all, really. What happens "on average" can be very, very different for each individual woman. I've had a total of 11 frozen embryos, and only 4 of those ever defrosted successfully. A much worse scenario than the one in ten your sister was quoted. I've also had three pregnancies from frozen embryo transfers, and I can't stress highly enough that my reasons for miscarrying those pregnancies were completely unrelated to the fact that those embryos had been frozen. They also quote a 42% pregnancy rate with blastocysts in women under 35... mine was 75%, so while I may luck out in one area, I certainly do look a lot more fortunate in other areas. Anyone else's IVF stats would look completely different again and probably be no closer to the quoted "averages".

If her little frostie bub makes it through the thaw, then there's every chance that it could work out. If the frozen embryo is from the same "batch" of embryos that produced a successful pregnancy, then there's an even higher chance that it could result in another baby for your sister.

BW