The copper wire changes the chemistry within the uterus and prevents the sperm from fertilizing the egg. It can stay in the uterus for up to five (5) years. Interestingly, the IUD is also used for "emergency contraception" to prevent ovulation within seven days of unprotected sex. While the precise mechanism of action of copper IUDs is still not certain, most likely the primary action is preventing the egg and sperm from meeting. The IUD may also interfere with the implantation of a fertilized egg. Some types of IUDs also release hormones (the so-called hormone mediated IUDs). In addition to the mechanism described above, the progestagen prevents penetration of sperm cells into the uterus.
Copper intrauterine devices (IUDs) are the most widely used method of contraception worldwide, yet in the UK only 5% of contraceptive users aged 16 to 49 currently use an IUD. This review will explore the patient and health professional factors that may explain the limited use.
In 1994-5 the Family Planning Association (FPA) surveyed more than 700 women aged 16 to 49 years to gain insight into how they chose their contraceptive method. They found that choice was highly individual and largely influenced by a woman's perceptions rather than characteristics such as age or parity. The majority of women approaching a health professional had already decided on their preferred method of contraception before the consultation.
A reluctance to use IUDs may be associated with myths and fears as indicated in table below.
| Women's concern | Evidence |
|---|---|
| Doubts about effectiveness | IUDs are over 99% effective. |
| Menstrual disturbance | Periods with an IUD are likely to be a day longer and heavier than without an IUD. |
| Pain | Periods with an IUD are likely to be more painful than without an IUD. |
| Infection | Risk is related to insertion and highest in the 20 days post insertion, risk is reduced by taking a sexual history and taking appropriate swabs. |
| Expulsion of the device | This is most common during the first or seconnd period after insertion; risk is reduced by the six week check and teaching women to check their threads. |
| Ectopic pregnancy | The absolute risk of ectopic pregnancy is extremely low due to the high effectiveness of IUDs. However, if a woman becomes pregnant with an IUD in place the likelihood of that pregnancy being ectopic is increased. |
| Infertility | There is a very low risk related to pelvic inflammatory disease, PID, (risk reduced by sexual history and swab taking) and ectopic pregnancy. |
A qualitative study from the current issue of the Journal of Family Planning and Reproductive Health Care looked at why women find IUDs unacceptable. One to one semi-structured interviews were conducted with ten women from an urban general practice, none of whom had ever used IUDs.
The study identified five main themes:
Many health professionals do not encourage the use of IUDs particularly in younger women. A contraceptive choice discussion should discuss all methods according to the user's medical eligibility. This was one of the key messages of the NICE guidance on long-acting reversible contraception.
There are very few WHO 4 (do not use) criteria for IUDs and they are as follows:
Common myths for health professionals and IUD use include that they are not suitable for:
The World Health Organization Medical Eligibility Criteria (WHOMEC) classify these women as follows:
With regards infection risk, the WHO recommend that IUDs should be left in place up to their maximum lifespan, because of the increased infection risk at the time of insertion. To reduce this risk as much as possible as health professionals we should take a sexual history.
If the woman is at a very low risk of STIs we should take swabs for Chlamydia and/or Gonorrhoea at the time of insertion. If the woman is at risk of infection we should take the swabs and wait for the results before fitting. If the woman is at risk and an IUD is being fitted for emergency contraception then we can consider prophylactic antibiotics to cover the fitting.
A systematic review published in February 2006 looked at all evidence related to IUDs, STIs and pelvic inflammatory disease (PID). It concluded that women with Chlamydia or Gonorrhoea at the time of insertion were at increased risk of PID, but the absolute risk was low:
References:
Asker et al. What is it about intrauterine devices that women find unacceptable? Factors that make women non-users: a qualitative study. J Fam Plann Reprod Health Care 2006; 32: 89-94.
National Institute for Health and Clinical Excellence. Long-acting reversible contraception CG30. 2005.
World Health Organization. Medical Eligibility Criteria for contraceptive use (third edition). 2004.
Family Planning Association. The intrauterine device (IUD)
Guillebaud J. Contraception - your questions answered. Churchill Livingstone. 2003.
Mohllajee A P, Curtis K M, Peterson H B. Does insertion and use of an intrauterine device increase the risk of pelvic inflammatory disease among women with sexually transmitted infection? A systematic review. Contraception 2006; 73: 145-153.