The woman may also have one or more orgasms during intercourse as well. Unlike a man, who usually can have only one orgasm during intercourse, a woman may have more than one. During intercourse she may rub her clitoris, or she may have her man do so. This can make the woman have an orgasm. The shaft of the penis may also stimulate the clitoris in some positions. Scientists are not sure why women have orgasms. Some believe that the orgasm helps the sperm in the man's semen to swim up the vagina into the cervix, so that it is more likely that a sperm cell will fuse with an egg cell. Others think that the woman's orgasm is designed to help make the man reach orgasm. During her orgasm, a woman may moan, cry, or scream, which usually excites her man, and her vagina may contract, gripping the penis more tightly and making sex more exciting for him. These reactions may cause the man to ejaculate more quickly or to produce more semen; when a woman reaches orgasm during intercourse, it often makes her man have an orgasm at that point as well. Orgasm may also encourage a woman to have sex more often as it feels good, increasing the chances of pregnancy. 