Mrs S,
Seeing as you got you pregnant while your Mirena was in, i thought that i should point this important information out for you.

If 1000 women used the Mirena for a year, only one would fall pregnant. This compares with about 10 for the normal IUD, 20 for the Pill and 10-15 for Depo Provera. This is comparable to the effectiveness of sterilisation.

Mirena acts as a contraceptive in two ways: it makes the mucus at the neck of the womb (the cervix) much thicker, preventing sperm from getting through and it also makes the lining of the womb extremely thin, stopping implantation. In some women it prevents ovulation.

If it does fail, there is a higher risk of ectopic pregnancy. If you felt pregnant or had a positive pregnancy test, it is important to see your doctor to rule this out. Overall, however, compared to women not using any contraception, the risk of ectopic pregnancy is greatly reduced (around 2 per 10,000 women each year because the Mirena is such a good contraceptive.

If a pregnancy does occur with a Mirena, it is advisable to remove the contraceptive if possible - this reduces the risk of bleeding, infection and miscarriage. Because failure is so rare, there is little information available on the effects on an ongoing pregnancy with the Mirena still in place.