the intentional prevention of conception by artificial or natural means. Artificial methods in common use include preventing the sperm from reaching the ovum (using condoms, diaphragms, etc), inhibiting ovulation (using oral contraceptive pills), preventing implantation (using intrauterine devices), killing the sperm (using spermicides), and preventing the sperm from entering the seminal fluid (by vasectomy). Natural methods include the rhythm method and coitus interruptus