[murphE]

I believe the Catholic position is, in vitro fertilization is OK, so long as all the embryos are implanted,

This is incorrect. The Catholic position is that in vitro fertilization is a grave moral evil.

[soccermom]

OK -- but the explanations I've read say it is a grave and moral evil because embryos are destroyed. If the embryos aren't destroyed, how can it still be considered a grave and moral evil?