The Levonorgestrel-releasing system Mirena, an intrauterine device ( IUD ), consists of a polyethylene T-shaped frame with a reservoir containing levonorgestrel.
Mirena is indicated for use as a contraceptive and, after insertion into the uterus, continuously releases Levonorgestrel at a low daily dose for up to 5 years.

Mirena's contraceptive action is due mainly to local progestogenic effects on the uterine cavity, including a strong antiproliferative effect on the endometrium and a thickening of the cervical mucus, which prevents the passage of sperm. Ovulation is inhibited in some women.

As of Nov. 28, 2005, the product monograph states that perforation or penetration of the uterus or cervix may occur during insertion but that this is very rare ( less than 1 in 10 000 ). It also states that postpartum insertions should be postponed until 6 weeks after delivery.

From Feb. 22, 2001 ( the date of marketing in Canada ), to Sept. 26, 2005, Health Canada received 26 reports of uterine perforation suspected of being associated with the use of Mirena.
In 8 of the cases, Mirena was inserted between 6 weeks and 6 months post partum.

A long-term prospective study of Mirena found a higher uterine perforation rate ( 0.9 per 1000 insertions) than that described in the product monograph.

With copper IUDs, the rate of uterine perforation has been 0.6-1.6 per 1000 insertions.
In addition, evidence suggests that women who have IUDs inserted in the first 6 months post partum are at increased risk of uterine perforation. This elevated risk may be due to the soft consistency of the uterus and the underestimated variability in uterine size during the first 6 months post partum.

Uterine perforation is a rare but serious complication of IUD insertion that occurs or is initiated at the time of insertion.
Evidence indicates that the rate of uterine perforation is lower in cases where the health care professional inserting the IUD has performed at least 10 previous insertions.
Currently, there is a shortage of health care providers trained in IUD insertion; access to good knowledge, proper equipment and a mentor to demonstrate and supervise several insertions are prerequisites to providing this service.

Health care professionals inserting the Levonorgestrel-releasing intrauterine system are encouraged to take this information into account. Special care should be taken with postpartum insertion, since perforations of the uterus have been reported.

Source: Health Canada, 2006


XagenaMedicine2006