<unk>  is 99–99.95% effective at preventing pregnancy, and is one of the most reliable, though not the most available, forms of birth control.<unk>  prevents pregnancy through multiple methods: by preventing ovulation, which means that no eggs are released for fertilization; by thickening the mucus of the cervix, which prevents sperm from entering; and by thinning the lining of the uterus, which makes<unk> ation of an embryo less likely. The way in which<unk>  causes these effects is by use of hormones. A small amount of the hormone progestin is released through the capsules continuously, more during the first year and a half, but then at a level similar to most contraceptive pills afterward. Like all hormonal contraception,<unk>  does not protect against sexually transmitted infections.<unk> able contraceptives are especially effective in the developing world, as they do not require daily administration or access to a hospital to be effective. In addition, no continual contraceptive supplies (pills, condoms, etc.) are necessary, and it is a highly effective, low cost contraceptive over the long term.
Levonorgestrel-releasing implant
High-dose estrogen
Extended cycle combined hormonal contraceptive
Lipoidal estradiol
Male contraceptive
5α-Dihydrolevonorgestrel
Estradiol-containing birth control pill
Cloxestradiol acetate