Only complete and consistent abstinence is 100% effective in preventing pregnancy and the protection against sexually transmitted diseases (STDs; also see the section on STDs).
Complete abstinence is defined as avoiding all types of intimate genital contact (including anal and oral intercourse). Consistent abstinence involves the practice of abstinence all the time. Some STDs spread through intimate skin-to-skin contact without actual penetration (for example, genital warts and herpes can be spread this way). Avoiding all types of intimate genital contact can thus prevent STDs. Abstinence does not prevent AIDS and Hepatitis B infections that spread via nonsexual activities like using contaminated needles for doing drugs, tattooing, or taking steroids.