Funnily enough, I have the polar opposite view. I generally oppose abortion, but I'm a staunch advocate of IVF with preimplantation genetic diagnosis tactics. In fact, I expect traditional procreation to be outlawed in this century.
Also either you're misunderstanding or explaining incorrectly. IVF does not require abortion unless you count the destruction of blastocysts as abortion. And if you do, I guess I don't see the moral difference.
The key moral difference in my opinion, and the reason I oppose abortion, is that it is the murder of a "future human". This also avoids the issue of "when is a fetus a human". IVF does not prevent a future human from existing, but abortion does.
I, like you, favor abortion for severe genetic disorders. IVF, of course, could avoid this problem entirely. I just hope progress in preimplantation genetic diagnosis isn't hindered by religious fundamentalists, it'd be truly evil.