Contraception: intra-uterine device (IUD)
What is an intra-uterine device (IUD)?
An intra-uterine device (IUD) is a small T-shaped plastic device that is inserted into the womb (uterus) to prevent pregnancy. A nylon thread is attached to the end of it so that it can be removed easily. IUDs currently available in Australia include the Multiload-Cu250 and Cu375, which have copper wire bound around the vertical stem, and Mirena, which releases a synthetic progesterone called levonorgestrel. IUDs are a long-term reversible form of contraception.
How does the IUD work?
The IUD works by preventing the implantation of a fertilised egg, as well as by helping to prevent the sperm from fertilising the egg in the first place by changing conditions in the uterus. It is thought that the body reacts to the IUD, causing a mild inflammatory reaction in the inside lining of the womb. There is also evidence that, with the Multiload IUD, the copper oxidises in the womb altering the environment in the uterus. Both these effects impede the movement of both the sperm and egg, as well as reducing their viability.
Mirena works by secreting levonorgestrel, a synthetic progesterone which is also used in the progesterone-only pill and some combined contraceptive pills. Progesterones thicken the mucus in the uterus and at the cervix and this makes it difficult for the sperm to swim and prevents them entering the uterus.
How effective are IUDs?
IUDs are about 99 per cent effective in preventing pregnancy, when replaced as recommended - usually every 5 years.
What are the advantages of an IUD?
The advantages of using IUDs for contraception are that they:
- are effective;
- allow fertility to return immediately upon removal;
- do not interfere with sexual intercourse;
- can be used while breast feeding;
- are relatively inexpensive;
- have no effect on your hormonal cycle;
- do not affect cholesterol levels or blood-clotting;
- require minimal ongoing attention; and
- may reduce heavy menstrual bleeding (Mirena).
What are the disadvantages of an IUD?
The disadvantages of using IUDs for contraception is that they:
- may cause periods to be heavier or longer (although this usually settles after a few months);
- may increase the short-term risk of pelvic inflammation following insertion;
- may not prevent ectopic pregnancy (where the fertilised egg implants in the fallopian tube instead of the womb);
- may perforate the uterus, although this is infrequent; and
- may be expelled undetected.
The popularity of IUDs decreased after the Dalkon Shield IUD was taken off the market in the 1970s. This recall was due to a higher than acceptable incidence of infertility and pelvic infections. Serious complications arising from IUDs rarely occur today.
In Australia, IUDs are mainly used in women who have already had a child, however, they can be used if you have never been pregnant. Occasionally, the insertion may be more difficult if you have not had children before. IUDs may not be suitable for women with multiple sex partners if there is an increased risk of acquiring a sexually transmitted infection, as this may result in pelvic inflammatory disease, which in turn may result in infertility. Similarly, those with a history of recurrent pelvic inflammatory disease or an ectopic pregnancy should discuss with their doctor the suitability of using an IUD.
How are IUDs used?
The device comes with an insertion tube that your doctor will use to place the IUD into your uterus. This is usually done between the last days of your period and the first few days following it, in order to reduce the risk of an undetected pregnancy.
It is recommended that every month after your period, you check that the string is able to be felt, to ensure that the device has not been expelled without you noticing.
Last Reviewed: 29 July 2009
- 1. World Health Organization. Medical eligibility criteria for contraceptive use. 3rd ed. Geneva: Reproductive Health and Research, WHO; 2004.
2. Stubbs E, Schamp A. The evidence is in. Why are IUDs still out?: family physicians' perceptions of risk and indications. Can Fam Physician 2008; 54(4): 560-6.
3. Skjeldestad FE. The impact of intrauterine devices on subsequent fertility. Curr Opin Obstet Gynecol 2008; 20 (3): 275-80.
