Contraception is the use of devices or techniques to prevent pregnancy. Oral contraceptives include the female contraceptive pill, a hormone preparation containing synthesized estrogen and progesterone, which prevents ovulation – the release of an ovum (egg) – and thickens the cervical mucus thereby reducing the chances of fertilization should ovulation take place. The convenience and efficacy of the various versions of the "pill" make it the most reliable form of contraception available, although it has been associated with some serious and some minor side-effects and should be prescribed on an individual basis.
Development of a male pill, containing testosterone and progestin is underway. Although initial tests have shown that it is effective in reducing sperm count, it will not be available for some years.
Barrier contraceptives include the male and female condom and the diaphragm. The male condom is a latex sheath which covers the penis and collects the ejaculated the semen; the female condom lines the inside of the vagina, preventing any sperm entering the uterus. The use of condoms is widely advocated because they help protect against some sexually transmitted diseases, including acquired immune deficiency syndrome (AIDS). Devices such as diaphragms and caps cover cover the cervix thus preventing sperm entering the uterus. The intra-uterine device (IUD) is a small spring made from plastic or metal inserted into the uterus. It stops the fertilized egg embedding itself in the uterine lining.
Emergency contraception, known as the morning-after pill, can be taken up to 72 hours after unprotected sexual intercourse; it prevents the fertilized ovum embedding itself in the uterus. It is not suitable to be used regularly.
Techniques to prevent pregnancy include the so-called "rhythm method". This involves the avoidance of intercourse on days when contraception is most likely (when the woman is ovulating). It is not a reliable method because ovulation cannot always be predicted accurately. Another technique if coitus interruptus – the withdrawing of the penis from the vagina before ejaculation. This is also very unreliable as small amounts of semen are also released from the penis before ejaculation.