Birth control, also known as contraception and fertility control, is a method or device used to prevent pregnancy. Different forms of birth control have different side effects and risk profiles. The choice of birth control method depends on many factors, such as the desire for reversible birth control (preserving future fertility) or permanent birth control methods (surgical sterilization). Some birth control methods, such as barrier methods, may offer some protection against sexually-transmitted diseases (STDs), while most methods do not. Some birth control methods have higher success rates than others, but no method of birth control is 100% effective in every case.