Birth control is the use of any practices, methods, or devices to prevent pregnancy from occurring in a sexually active woman. Also referred to as pregnancy prevention, fertility control, or contraception; birth control methods are designed either to prevent fertilization of an egg or implantation of a fertilized egg in the uterus. Birth control has been used since ancient times.There are many methods for birth control. The most effective methods of birth control are sterilization in both males and females, intrauterine devices (IUDs), and implantable birth control. This is followed by a number of hormone-based methods including oral pills, patches, vaginal rings, and injections.Less effective methods include physical barriers such as condoms, diaphragms and birth control sponges and fertility awareness methods. The least effective methods are spermicides and withdrawal by the male before ejaculation.