PIP: The condom is a latex rubber sheath worn over the erect penis during sexual intercourse, designed to prevent conception and the transmission of sexually transmitted diseases (STDs). Any one condom is meant to be used for only one complete act of intercourse. This method is highly recommended for sexually active adolescents. Should a condom tear during intercourse, the woman should seek emergency contraception to avoid pregnancy. A spermicide should be applied immediately to help reduce the likelihood of STD and HIV transmission. Vasectomy involves excising the vas deferens, severing the route through which sperm passes from the testes and conferring a permanent method of male contraception. Withdrawal involves interrupting sexual intercourse prior to ejaculation, while periodic abstinence refers to not engaging in sexual intercourse during a woman's ovulation period. The calendar, temperature, Billings, and sympto-thermal methods may be used to determine a woman's fertile period.