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The Intra-uterine Device (IUD)

The intrauterine device (IUD) is a small plastic device that is fitted within the uterus in order to prevent pregnancy. The standard IUD is coated with copper. A newer form of IUD releases progesterone and is often referred to as the intrauterine system (IUS), as it combines two contraceptive methods, the intrauterine device and the hormone.

The IUD exists in many forms around the world, with availability differing by country. There are small variations in size, composition, and method of insertion. For example, the Gynefix, which is unavailable in the U.S., is inserted so that the tip is embedded in the uterine wall.

The IUD is inserted via the cervix in a compressed manner and opens to its full shape (often similar to the letter T) inside the uterus. When open, the IUD is wider than the opening of the uterus and thus should remain in place until medically removed. Two small strings are left protruding from the cervix to allow confirmation that the device has not spontaneously slipped out. These strings also facilitate removal when desired.

The efficacy of the IUD in prevention of pregnancy is approximately 99%. It remains effective for a number of years, depending on the brand. For example, Paragard (the IUD currently available in the US) is approved for 10 years of use and the Mirena IUS is approved for five years.


The exact mechanism of the IUD is still not completely understood. The most recent and widely accepted theory is that the copper-coated IUD prevents conception by altering the environment within the uterus and fallopian tubes so that fertilization cannot take place. The IUD was once thought to prevent implantation, i.e., the sperm and ovum unite and begin dividing but the resulting embryo does not become embedded in the uterine lining. This earlier theory appears to be accurate in  only a small minority (about 1%) of cases.

The IUS works like other progesterone-only contraceptives by suppressing ovulation and altering the cervical mucus, thus preventing fertilization. In addition, the presence of a foreign body in the uterus seems to interfere with both fertilization and implantation.


In the decades that IUDs have been available, a number of health concerns have been raised. In the 1970s there were cases of death associated with the use of one brand of IUD (the Dalkon Shield). This has not been reported with currently available devices, despite their very common use world wide. Older studies raised the fear of increasing pelvic inflammatory disease, which could lead to sterility due to blockage of the fallopian tubes from post infection scarring ("tubal infertility"). Recent studies with the new copper intrauterine devices have found no increase in tubal infertility and an overall low rate of pelvic inflammatory disease. Another concern raised with the IUD was whether it increases the incidence of ectopic pregnancy (pregnancy outside the uterus). Recent studies seem to indicate that the device does not cause ectopic pregnancies, but does a better job preventing uterine pregnancies than extra-uterine pregnancies. Currently, the IUD is felt to be a safe and efficacious method of contraception and is in fact the most common method of reversible female contraception outside the US.

Bleeding and Staining

Menstrual blood loss increases by approximately 50% during use of the copper IUD. This can either be heavier menses or irregular bleeding. Heavy menses result in additional days of staining before a woman can do a hefsek taharah. Irregular bleeding can cancel out the blood-free days that she has counted so far, leading to prolonged periods of niddah, or can make her a niddah again soon after she has immersed in the mikveh. Some women may also experience changes in the length of the menstrual cycle.

The IUS over time reduces the amount of bleeding experienced during menstruation by around 80% on average, and may eliminate menstruation altogether. However, many women experience irregular bleeding or spotting on initiation of this method.

The degree of irregular bleeding decreases over a number of months of use and for most women it reaches acceptable levels within 3-6 months. However, women who use either an IUD or IUS need to be prepared for a difficult beginning, and should take precautions to avoid becoming niddah unnecessarily due to staining (see Ketamim).

Halachic Desirability

The different theories as to the mechanism of action and past health concerns have had implications for the halachic desirability of this form of contraception. If the IUD primarily prevents fertilization, then it presents few halachic problems in a situation where contraception itself is permissible. On the other hand, if the IUD prevents implantation of the fertilized ovum, then the more serious issue of abortion is raised. Furthermore, health risks are always a halachic concern. Currently, the IUD is considered by many rabbis to be the method of birth control second in line after hormonal contraception, although controversy does exist.

The halachic implications of the IUD insertion procedure are discussed in a separate article.

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Information for your Health Care Provider


Click on the link(s) below for related articles from Jewish Women's Health, Nishmat's website for medical professionals. You may find it helpful to share this information with your physician by printing or emailing relevant articles,
or by accessing the site during your appointment.

  Intrauterine Device
Halachic Considerations in Contraception

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