Conception
Conception requires multiple events to take place. To begin with, sperm has to enter into the vagina and travel to the cervix. Next, it needs to come into contact with a mature egg and fertilize it. The fertilized egg has to travel to the uterus and implant itself in the uterine lining, where it can then mature into a fetus. There are many different methods of birth control and each try to prevent different steps within this process.
Spermicides and Barriers
Some birth control works on preventing sperm gaining access to the egg. Some of these methods include spermicidal agents. These chemicals, which can come in jelly or foam form, work to kill off sperm before they can fertilize an egg. Other methods of birth control simply work to prevent sperm from gaining access to the cervix, also known as birth control barriers. These barriers, which include condoms and contraceptive sponges, block the sperm and prevent them from getting through the vagina. These barriers also include medications that thicken the mucus that the cervix produces, making it harder for the sperm to get through. These forms of birth control are typically called physical barriers, whereas spermicides are called chemical barriers.
According to the American Congress of Obstetricians and Gynecologists, although a single barrier is not as effective as some other methods of birth control, combining a chemical and a physical barrier (i.e. spermicide and a condom) are highly effective. One drawback of using barriers, however, is that they can malfunction or break. They also aren't effective if they are not used properly, which may require practice and checking to make sure that the barrier is intact.
Hormonal Methods
Other methods of birth control focus more on the female's reproductive cycle. The female menstrual cycle is responsible for the release of mature eggs and then for the subsequent implantation of a fertilized egg into the uterus. Hormonal birth control works on disrupting the new hormonal cycle that governs the release of mature eggs and their implantation. Hormonal birth control can come in the form of a patch, pills, rings and injections. These methods cause the steady release of hormones such as estrogen and progestin. These hormones regulate the rise and fall of other hormones that allow a woman to release an egg and be fertile.
Hormonal birth control has the advantage of being extremely effective (the Family Health Initiative indicates that hormonal birth control is 99 percent effective when used correctly), they can have certain side effects (such as weight gain and an increased risk of blood clotting). They also do not protect against sexually transmitted diseases. There is also a risk that taking antibiotics can interfere with hormonal contraceptives, making them less effective.
