The intrauterine device (IUD) is a form of birth control; it is an object, placed in the uterus, to prevent pregnancy. Among modern IUDs, the two types available are copper-containing devices, and a hormone-containing device that releases a progestogen. Currently, there are over 10 different kinds of copper IUDs available in different parts of the world, and there is one hormonal device, called Mirena.
Names and descriptors of intrauterine contraceptive devices vary by location.
In the United States, there are two types of intrauterine contraceptive available: the copper Paragard and the hormonal Mirena. Both of these contraceptives are referred to as IUDs in the United States.
In the United Kingdom, where over ten types of copper-containing IUDs are available, the term IUD only refers to inert or copper-containing devices. Hormonal intrauterine contraceptives are considered to be a different type of birth control, and they are distinguished with the term intrauterine system or IUS.
The WHO/ATC name is IUD for both copper and hormonal devices.
Most non-hormonal IUDs have a plastic T-shaped frame that is wound around with pure electrolytic copper wire and/or has copper collars (sleeves). The Paragard T 380a is 32 mm (1.26") in the horizontal direction (top of the T), and 36 mm (1.42") in the vertical direction (leg of the T). In some IUDs, such as the Nova T 380, the pure copper wire has a silver core which has been shown to prevent breaking of the wire. The arms of the frame hold the IUD in place near the top of the uterus.
Other shapes of IUD include the so-called U-shaped IUDs, two examples are the Load and Multiload. These are similar to the T-shaped IUDs, in that they have a plastic "leg" running vertically, but at the top, rather than two straight horizontal arms, they instead have two arms that curve downwards towards the "foot" of the device.
Another shape of IUD is the frameless IUD. GyneFix does not have a hard plastic shape of any kind. Rather, it has a plastic string (similar to fishing line) that holds several hollow cylindrical copper beads. (Gynefix 330 with 6 and Gynefix 200 with 4) GyneFix is held in place by a suture (knot) to the fundus of the uterus. This particular IUD is favored by many women as it can flex, and move with the uterus as it changes through the course of the menstral cycle while still having the advantages of a copper IUD. Gynefix also has very low expulsion rates due to it being the smallest IUD currently available. Gynefix is mainly available in China, Europe, and Germany, although some clinics in the USA and Canada can provide it. ( Womens Willow Clinic Can http://www.medicalabortion.ca/?page_id=22 ) Gynefix is removed like most other IUDs using forceps but is actually pulled out from the Fundus.
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