There are many safe and effective birth control methods available to women either at the pharmacy (condoms) or the doctor's office (the pill). Those of us who need birth control want to find the best method for our sexual lifestyle. Contraceptives prevent unwanted pregnancy by blocking sperm, disabling sperm before it reaches the uterus, or suppressing ovulation, but how exactly does each one work?

In TED-Ed's video, "How do contraceptives work?" host NWHunter explains the mechanics behind the different kinds of contraceptives during sex.

Pregnancy occurs during sexual intercourse when the sperm swims up the vagina through the cervical opening, up to the uterus and into one of the two fallopian tubes. If an egg is released during that month's ovulation, one sperm has a chance to fertilize it.

To prevent this process, some contraceptives like condoms use the "block" method. Male and female condoms act as a barrier to prevent sperm from coming into contact with the vagina. Unlike other contraceptive methods, they are able to prevent transmission of certain sexually transmitted diseases as well. Although condoms are 98 percent effective with perfect use, they're only 82 percent effective in practice.

Meanwhile, contraceptives like the diaphragm, cervical cap, and sponge work by being placed over the cervix, barricading the entrance to the uterus. These contraceptives are sometimes called “barrier methods,” and can be used with spermicides — a chemical that immobilizes and destroys sperm. Spermicides are also an example of the second category: disable. Spermicide is only 85 percent effective, even with perfect usage, and just 71 percent effective with typical usage

Lastly, hormonal contraceptives like the pill, the patch, the depo shot, and the vaginal ring all release synthetic versions of various combinations of progesterone and estrogen. This hormone cocktail suppresses ovulation, keeping the immature egg safely sequestered in the ovary. The patch and pill are 99 percent effective when they're used perfectly, but in practice, that's 91 percent.

Scientists are currently researchin new methods, such as a male pill that would prevent sperm production.