in the late 20th century, very effective forms of contraception (birth control) were developed allowing a man and women to help prevent a baby from being made when they have sex. one type of contraception is a condom. this is a piece of rubber that covers the penis that a man can wear during intercourse, which stops the man's semen from going into the woman's vagina. this does not always work though because the condom may rip or tear. another well-known type of contraception is called the pill, which a woman takes every day. when a woman is "on the pill," she and her partner may have sex any time they wish with very little chance of making a baby. it is recommended that a couple who have a sexual relationship use two forms of contraception. that way if one fails the other is a 'backup'.