Pro-Life Blogs had a story a while back about "Birth Control Is Harmful" billboards springing up all over a midwestern city in response to the local Planned Parenthood affiliate's "Birth Control Is Easy" billboards. The anti-contraception billboards were placed by a local Catholic "Respect Life" organization.
Although most of the group's argument applies to the way contraceptives enable and encourage sex outside of marriage, their website also claims:
Contraception is harmful to marriages. Only four years after contraceptives were first tested, researchers found that marriages in which contraceptives were used were twice as likely to end in divorce as marriages in which there was no contraceptive use. Why this huge difference? Well, using contraceptives means that a couple's fertility is suppressed, and treated like a disease. They are no longer able to share themselves with each other totally in the sex act. There is a barrier not just physical, but also emotional, erected between them. They are closing one part of themselves off from each other, and from God. Often the couple begins to be dissatisfied. The wife starts to feel that the husband does not desire her, only her body. The husband begins to feel that his wife does not really want to have sex with him, that she is cold and tired. These attitudes can poison their whole relationship. With this crucial part of their marriage gone bad, other problems soon develop.
Four years after contraceptives were first tested? They must mean something modern like The Pill, not any age-old method of trying to prevent conception. I would suggest that anyone using the pill four years after it was first tested should be considered an early adopter, likelier to have a non-traditional mindset than those who would follow much later. So they might also be more inclined to bail out of marriage.
But that stat is really just there to bolster the dogmatic point. While sex has both a unitive and procreative purpose -- something most Christians would agree on -- Catholics argue that sex cannot be truly unitive unless it is also procreative. And that isn't just the totality of a couple's sex life, but each individual act. As Pope Paul VI said in his encyclical on the subject, Humanae Vitae:
Consequently, it is a serious error to think that a whole married life of otherwise normal relations can justify sexual intercourse which is deliberately contraceptive and so intrinsically wrong.
Other Catholic sites dealing with contraception and sexuality: No Room for Contraception blog, Theology of the Body (Christopher West's website).