Any birth control method is only as good as the person using it. So, for instance, don't expect your birth control pill to prevent pregnancy as well as it does in studies if you don't take it as directed. And don't expect a condom to work up to 90 percent of the time (as studies show) if your partner doesn't put it on properly or use them every time you have intercourse—or come close to having intercourse.
The most effective forms of birth control are abstinence—not having sex—or sterilization. There are three forms of sterilization: vasectomy for men, in which the tubes through which sperm move into the penis are blocked or cut; tubal ligation for women, in which the fallopian tubes are blocked, burned or clipped shut; and Essure procedure for women, in which micro-inserts are placed into the fallopian tubes where they form a tissue barrier that prevents sperm from reaching the egg. Each is considered nearly 100 percent effective, and each is permanent.
The intrauterine device ParaGard also prevents pregnancy more than 99 percent of the time, and it can remain in place for up to 10 years. Another intrauterine device called Mirena has a similar efficacy rate, but it also releases the hormone progestin into your body. It may remain in place for up to five years. Another option in the 99-percent-or-more-effective category is Implanon, a tiny rod that is inserted into your arm where it releases a continuous amount of progestin to prevent pregnancy. It can remain in place up to three years.
Other hormone-related options, including birth control pills, the OrthoEvra patch, the NuvaRing vaginal ring and progestin injections like Depo-Provera, are considered "very effective," meaning they prevent pregnancy 91 to 99 percent of the time. Depo-Provera works for three months; the others for one month.
These invasive options are followed by more moderately effective options, which typically prevent pregnancy 81 to 90 percent of the time. They include male and female condoms, the Today Sponge and a diaphragm.