The Mirena consists of a small, plastic T-shaped frame with 2 fine threads attached to the base which is inserted into the womb and carries progestogen hormone in a sleeve around its stem. The progestogen is released gradually into the uterus and a special covering on the hormone sleeve controls the rate of release. A gradual release of progestogen acts on the lining of the womb by suppressing its formation which reduces and eventually stops the menstrual bleed.
As the Mirena delivers progestogen directly to the cells of the lining of the uterus (endometrium) it protects against abnormal cell changes. In some women the ovaries are also affected by the gradual absorption of the progestogen which results in the cycle being suppressed (usually around 3-6 months after fitting) and therefore the cyclical swings in oestrogen production are controlled.
The Mirena is also a very reliable method of contraception with studies showing that if 1,000 women use the system for one year, no more than 2 become pregnant. This figure is similar to the figure for sterilisation with the added benefit that you are protected from pregnancy as soon as the system is fitted.
Most women can use the Mirena but occasionally it will simply not be suitable or may be too difficult to insert.
The Mirena now has its licence to remain in place for 5 years and may be removed at any time during this period. Fertility would be expected to return to normal within a month or two of the removal.
There are two different types of device that are often referred to as "coils". The first is an IUD (intrauterine device) made from plastic and copper which is only used as a form of contraception and has no hormonal content. The other type is the IUS (intrauterine system) which is most commonly referred to by the brand name "Mirena". The Mirena is not only a reliable form of contraception, but also contains progestogen and is therefore particularly useful in treating some hormonal symptoms.
Only a doctor or a specially trained nurse can fit the system. It is fitted into the uterus through the vagina after inserting a speculum (similar to that used for a cervical smear). Occasionally the use of a local anaesthetic in the cervix (neck of the uterus) may be required.
Most women find that the fitting of the Mirena causes only a little discomfort; however, for some it may be uncomfortable. It may be advisable to use a painkiller an hour or two before the fitting. Preparation for the fitting usually takes about 5 minutes but the actual fitting takes only a few seconds.
The system is usually fitted either during your period or within 7 days from the beginning of your period. Once the Mirena has been fitted you can check yourself to make sure that it is still in place and Mr Curtis will show you how to do this.