There are three types of T-shaped IUDs now available; Skyla, Mirena, and Paragard. All three provide very reliable and convenient long acting, but quickly reversible, contraception. Almost all women are eligible candidates to use them. (Click on each type of IUD above to get more information from the manufacturers.)
All of them may be replaced immediately with a new IUD when they are removed. The Skyla IUD is smaller than the Mirena, and may therefore be a good option for a woman who has never had children and is thus likely to have a small uterus.
IUDs do not prevent ovulation or the formation of ovarian cysts. They work primarily by inhibiting sperm motility and viability to prevent fertilization. They may also change the transport speed of the egg through the fallopian tube. It is possible that they sometimes may damage a fertilized or unfertilized egg and prevent implantation. Progesterone-containing IUDs have two additional mechanisms of action. They increase the thickness of cervical mucus, making it more difficult for sperm to enter the uterus. Progesterone also suppresses the buildup of the uterine lining. Consequently, periods tend to be less frequent, lighter and shorter (or sometimes non-existent). Some women will have hormone related side effects including headaches, nausea, breast soreness and depression. In contrast, the copper IUD is usually associated with longer, heavier, more painful periods and can also cause bleeding in between periods. Fortunately, these symptoms often decrease over time.
The Mirena and Skyla IUDs contain progesterone, while the Paragard is non-hormonal, and contains copper. Paragard is less costly.
The three IUDs are approved for different lengths of time as follows: Skyla for up to 3 years, Mirena for up to 5 years, and Paragard for up to 10 years.
Complications are uncommon with IUDs but include expulsion (2-10% during the first year of use), perforation of the uterus during insertion (1/1000), and unintended pregnancy (0.2% annually for Mirena and Skyla, and 0.8% annually for Paragard).
If pregnancy does occur with an IUD in place, the pregnancy is more likely to be ectopic (outside the uterus). IUDs do NOT increase the risk of ectopic pregnancy. However, ectopic pregnancy is a life-threatening condition and must be medically or surgically treated.