#MIRENA IUD #contraception #excessiveMenstrualBleeding #heavyPeriods Mirena Intrauterine Devices remain a popular method of long term contraception in women wishing to avoid or delay childbearing. Mirena, available since 2000, provides at least 5 years of worry free contraception. In addition to contraception, Mirena dramatically reduces the amount of blood loss in women suffering from heavy menses. It may provide additional benefit in women with PCOS or endometriosis. Mirena functions by thickening the cervical mucus and preventing passage of sperm into the uterine cavity. In addition it appears to prevent sperm capacitation or the changes necessary to allow penetration into the egg. Mirena may alter motion of the sperm and cause thinning of the lining of the womb. The progesterone acts locally rather than systemically. Women of childbearing potential may opt for the Mirena IUD. Prior childbirth is not a requirement. The device does not prevent sexually transmitted infections and unlike the copper containing device does not provide post-coital or emergency contraception.