Even When Used Correctly, Contraception Isn't Foolproof
"Contraceptives are very effective when used correctly and consistently," says Barr. While they aren't 100 percent guaranteed, they are very close; most are better than 90 percent effective. Among the most effective methods are implantables, like implantable rods or IUDs, and vasectomies. In the first year of typical use, both these methods reduce chance of pregnancy by nearly 100 percent, according to the CDC. By comparison, the pill, male condoms, and withdrawal have failures rates of around nine, 18, and 22 percent (respectively) in the first year of typical use.
A recent Guttmacher Institute report gives a good picture of how greatly contraception can affect pregnancy rates. Looking only at women who are at risk for unintended pregnancy, the report found that two-thirds of these women use contraception consistently and correctly throughout the year and, as a result, accounted for only five percent of unintended pregnancies. However, women who use contraception inconsistently or incorrectly account for 43 percent of these pregnancies. The remaining 16 percent — women who do not use contraception for a month or more — make up 52 percent of all unintended pregnancies.