Contraception (birth control) prevents pregnancy by interfering with the normal process of ovulation, fertilization, and implantation. There are different kinds of birth control that act at different points in the process.
All forms of birth control have one feature in common. They are only effective if used faithfully. Birth control pills work only if taken every day; the diaphragm is effective only if used during every episode of sexual intercourse. The same is true for condoms and the cervical cap. Some methods are automatically working every day, no matter what. These methods include Depo Provera, Norplant, the IUD, and tubal sterilization.
Contraception aims to prevent pregnancy.
keeping the egg and sperm apart
stopping egg production
stopping the combined sperm and egg (fertilised egg) attaching to the lining of the womb
A woman can get pregnant if a man’s sperm reaches one of her eggs (ova).