The first reason is that the use of contraception leads to abortion. That is, they cause early abortions. All oral contraceptives, Norplant, Depo-Provera, and IUDs cause abortions before a woman even knows she's pregnant. According to Dr. Bogomir Kuhar, in Infant Homicides Through Contraceptives, these forms of birth control take an estimated 8.1 to 12.75 million lives each year. Contraceptives also cause abortions through their failures.
All contraceptives fail, some quite often.
Even surgical sterilization has a failure rate. Although the failure rates may be fairly low, still the fact that they even exist should be a warning. These pregnancies are much more likely to end in abortion. C ontraceptives made the sexual revolution possible. Once people discovered that they could have sex without the possibility of pregnancy, or with a greatly reduced risk of pregnancy, they began to disregard the traditional structures that had protected children and sex for centuries.