Mirena, available in Europe for the last 10 years, could help rejuvenate IUD use here, says Lawrence Finer, a senior research associate at the Alan Guttmacher Institute, which specializes in reproductive health issues. Mirena proponents are also enthusiastic about the product's effects on menstruation. For the first few months, Mirena may cause irregular or heavy bleeding. But then a woman's period may become shorter and lighter, stopping entirely for 20 percent of users. Blumenthal says this is not harmful.
Periods resume when they stop using the device.
But there are some potential drawbacks. There is some evidence, for example, that levanorgestrel-like hormones, similar to the one released by Mirena, are associated with an increased risk of breast cancer if used together with other hormones, says Roberta Ness, an epidemiology professor and director of the women's health program at the University of Pittsburgh. But such hormones may also decrease the risk of ovarian or endometrial cancer, she says. Any cancer risk from Mirena would likely be much smaller than the risk of oral contraceptives or from Norplant or Depo Provera, which involve much higher levels of the same hormone. In any case, anyone with known or suspected breast cancer should not use Mirena, the FDA says.