The Catholic Church (or any Church) will have some moral stands which are in fact universal: that is, not based upon distinctive supernatural doctrines, but based on a careful consideration of justice and humanity. This kind of moral stand is called Natural Law: not because it's based on general animal nature (zoology), but because it's based on "natural" reason and the requirements of human nature and which is applicable to everyone.
To illustrate: if the Catholic Church says, "There's an obligation to go to Mass on Sunday," that's based on something distinctive to one church (Mass) and a supernatural doctrine (that the Lord was raised from the dead on a Sunday.) But if the Church teaches that selling your children into slavery is wrong, it's because the child has the same nature that you do, and is to be treated as "person" and not as "property."
To put it briefly, every person's secure sense of identity and belonging is based on his parentage. Under conditions which are natural to the human race, your genetic mother, your gestational mother, your social mother and your legal mother are the same woman; your genetic father, social father and legal father are the same man (and is married to your mother.) That is the physical basis for security and stability for the child.
If anything goes inadvertently wrong here --- a parent dies, or a child is conceived by parents who can't raise the child --- then other arragements (such as adoption) have to be made in response to the needs of the child.
But it would be wrong to deliberatly bring a child into existence via a process where his very sense of identity will be intentionally "fractionated."
Some of the assisted reproductive technologies just help infertile parents overcome their infertility and then have children through marital intercourse: this is fine. But to premeditatedly bring a child into existence missing a chunk of his parental birthright is unjust to the child: it's depriving him of the normal set of "identity coordinates" that everybody has a right to.
A more detailed ethical discussion can be found here:
http://home.comcast.net/~icuweb/c04109.htm
A shorter and more personal take by Eve Tushnet is here:
http://www.ncregister.com/articulo.php?artkod=ODg=
"To put it briefly, every person's secure sense of identity and belonging is based on his parentage."
I was adopted as an infant under the old (and I believe, superior) "closed" adoption method. I have no idea who my biological parents are, and I don't know if I'm biologically related to anyone living on this planet. I also don't care, because my adoptive parents were terrific. So I consider that point to be horse hockey (to put it as sweetly as possible).
IVF uses biological material from at least one of the parents, so there's at least a biological connection, and you can't say that people willing to go through such an arduous and expensive method to become parents are not doing it with a great deal of thought and purpose. So if you and your church don't like it, fine, but I don't see people demonstrating loudly outside of IVF clinics to stop the procedure, or marching on Washington to end the tragedy of IVF.