WOMEN’S BODIES: INTRAUTERINE DEVICES

Intrauterine devices (IUDs) are inserted into and retained within the uterine cavity to prevent conception. The IUD was the first reversible contraceptive method that required just one action – its insertion -to provide long-term contraception.

History of the IUD

The first story (unverified!) concerns nomadic tribes in North Africa thousands of years ago, who are said to have placed stones in the uteri of camels to prevent pregnancy during long treks. Over 2000 years ago Hippocrates, the father of medicine, is reported to have recommended inserting objects into the uterus for contraception.

The first modern IUD dates from 1909, with descriptions of coils of silkworm gut used in Europe. The first widely used IUD was the Gräfenberg ring, developed in Germany in the 1920s. It was made of coiled silver-copper alloy wire. The ring gained a bad reputation at the time because of the high rate of infection and other complications when it was inserted by untrained operators, and also perhaps because contraception was strongly condemned by political authorities in Germany at the time. It has since been shown that, with proper insertion and care, the Grafenberg ring can be as safe as any other IUD and it remains the most commonly used device worldwide (because it’s so popular in China).

The first plastic device was introduced in 1962, the first copper-carrying device in 1969, and the first hormone-releasing device in the mid-1970s. Today it’s estimated that more than 60 million women worldwide used IUDs, over 40 million of them in China.

Because IUDs must pass through the narrow cervical canal to be placed in the uterine cavity, ingenious designers have come up with a variety of forms that may be folded, straightened or compressed in some way for insertion but are able to regain their shape within the uterus. The effects of adding copper or hormones to IUDs is described below.

How do IUDs work?

Nobody’s quite sure, but IUDs are believed to prevent pregnancy in the following ways.

• Their presence as a foreign body causes a reaction in the lining of the uterus that makes it unsuitable for implantation of a fertilised ovum.

• Recent studies suggest that the changes in the uterus – both in the fluid contained in it and in its lining – prevent sperm from swimming through its cavity to fertilise the ovum.

• Copper causes a foreign-body reaction together with other changes in the endometrium, making it even less suitable for implantation. Copper is also toxic to sperm.

• Progestogen-releasing IUDs alter the growth and development of the endometrium in each cycle. Progestogen also affects cervical mucus so that sperm are less able to pass through the cervical canal.

The contraceptive efficacy of plain plastic IUDs depends on the surface area of the device that is in contact with the endometrium. With the added effects of copper or hormones, smaller devices are as effective as larger plain devices.

How effective are IUDs?

For all devices used now, failure rates are 0.3-6 pregnancies per hundred woman-years. Copper and hormone-releasing devices are generally more effective. About one-third of failures are due to undetected expulsion of the IUD. The most important factor that influences efficacy (and other problems) is the degree of skill used in inserting the device.

Side-effects and j complications

The most common side-effects are heavier periods, longer periods, menstrual cramps and spotting between periods. These menstrual side-effects tend to be worse soon after insertion and usually, but not always, settle down after a few months. About 15 per cent of users have the device removed within two years because of its effects on menstruation.

Less common side-effects are cramps between periods and cramps or pain after orgasm. IUDs have no side-effects on the rest of the body.

There can be complications: the main worries are pregnancy and pelvic infection.

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