The intrauterine device (IUD) is a small contraceptive device fitted within the uterus. It needs to be inserted and removed by a physician. Depending on the type, it can be effective for 3-10 years.
Types of IUD
There are two main types of IUD. The copper IUD is made from plastic and copper. The hormonal IUD (also known as the intrauterine system, or IUS) is a plastic device that releases synthetic progesterone. Both types of IUD are over 99% effective.
Each type comes in a range of forms, with availability differing by country. There are small variations in size, composition, hormonal formulation, and method of insertion. A T-shape is most common. In attempts to reduce irritation, Ballerine is ball-shaped, and the Gynefix (currently less widely available) has its tip embedded in the uterine wall.
Mechanism
The exact mechanism of the copper IUD is still not completely understood. The most recent and widely accepted theory is that it prevents fertilization by altering the environment within the uterus and fallopian tubes so that it is hostile to sperm.
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 very small minority of cases.
The IUS works like other progesterone-only contraceptives by suppressing ovulation and altering the cervical mucus, thus preventing fertilization. In addition, as above, the presence of a foreign body in the uterus seems to interfere with both fertilization and implantation. All types of IUS release the synthetic progesterone levonorgestrel, although at different dosages.
A physician inserts the IUD or IUS into the uterus through a narrow applicator tube, which is generally less than 10 mm in diameter. The IUD/IUS opens to its full shape inside the uterus. When open, the IUD/IUS is wider than the opening of the uterus and thus should remain in place until medically removed.
After insertion, the IUD/IUS requires no further action on the part of the couple. One or 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.
Safety
Intrauterine devices are considered a safe and efficacious contraceptive method. In many countries, they have become the most popular method of reversible female contraception.
Recent studies with modern copper IUDs have found no increase in tubal infertility and an overall low rate of pelvic inflammatory disease, which were of concern with some older versions.
Concerns have been raised in the past as to whether the IUD increases the incidence of ectopic pregnancy (pregnancy outside the uterus). Recent studies seem to indicate that the device does not cause ectopic pregnancies, but rather prevents uterine pregnancies more effectively than extra-uterine pregnancies.
Side Effects
Both the IUD and IUS are associated with irregular bleeding and staining, which we discuss in detail below.
Additionally, the copper IUD is often associated with heavier and/or longer menses. Some women also experience changes in the length of the menstrual cycle.
The hormonal IUS is often associated with prolonged staining. It also can have other side effects common to progesterone-only contraception, including mood changes (especially depression) and weight gain. However, as the progesterone is release locally and not taken systemically, the frequency of these side effects is believed to be less than when taken orally.
Over time, the hormonal IUS significantly reduces the quantity of menstrual bleeding, and may eliminate menstruation—and niddah—altogether.
