She writes:

I have a question for you. I have a couple of non-Catholic neighbors, friends trying to conceive. They've already frozen eggs. Is it improper if me, a Catholic, to pray for success with the implantation of the embryos? Thanks for your time...

Hmmm.This is one of those things the apostles and fathers of the Church never had to think about.   I think the first thing to do, if possible, is try to broach with them the question of the morality of IVF. Have you spoken with them about the moral implications of what they are doing? IVF involves fertilizing multiple eggs, picking one for implantation, and then killing the rest.  In short, selective abortion. Perhaps your relationship with them might allow that conversation to happen?  I don't know. If you can't stop them from doing something fundamentally immoral, you can only pray for God to bless and prosper the innocent child who will result from this sinful act, not for the sinful act itself. You can always pray for God's redeeming power to be displayed over this sin and that the parents realize it is a sin and repent of it.

By the way, a side note, not for my reader's : I have run across Catholics with the superstitious fear that children resulting from IVF or (should we get there) cloning could be "born without souls".  This is not the case.  To have a soul is, in Catholic understanding, to be alive.  If you are alive, you have a soul. Thus, all living things have souls: plants have souls proper to their nature, dogs have doggy souls, pigs have piggy souls--and humans have human souls.  No soul, you're dead.

Souls are not given us by our parents but are created directly by God.  So however one's body comes into the world, one's soul is made by God.  And, truth to tell, clones are nothing new in nature.  Every identical twin as a kind of clone created when a newly fertilized zygote is split in two and results in two genetically identical embryoes developing.  One of the minor puzzles in theology involves the question of what the body/soul relationship is, since the splitting of the zygote occurs after conception and therefore presumably after ensoulment.  I resolve the matter by saying "God, under carefully controlled laboratory conditions, can do whatever the heck he wants."

This is not, by the way, to say that human cloning would be morally acceptable.  There are all kinds of insuperable moral barriers against it.  As clone experiments with other animals have demonstrated, cloning and conception are not the same.  When you clone cells from old animals rather than uniting sperm and egg as God intended, you wind up with clones who develop all kinds of health problems prematurely.  However, even if that technological problem were overcome and you created babies who were perfectly heatlhy, the central moral question would always remain: Babies are persons, not products of manufacturing.  Reducing them to products of technology will be wrapped in a promising lie of reproductive hope, but it will really mean that the manufacturer owns the child and therefore will have the right to treat her as a thing and not a person.  The old word for that is "slavery".  If you want to know what a technological civilization embracing the power to engineer persons to spec looks like, read Brave New World.

The Church's teaching here, as ever, is sane in our insane world.  Just as children are a divine gift that no man can take away by murder, so they are a divine gift that no man should wrest from God by any technological force that destroys the unitive or procreative nature of marriage.  The moment human beings cease being received as gifts and start being products of anti-natural technology is the moment fallen man claims the right to own and manipulate and, if he desires, kill and harvest them (among many other uses industry has found and will find).  

Moral: Catholics should learn about and share information on legitimate forms of fertility treatment.