What are the known side effects of the Mirena IUS?

The U.S. Food and Drug Administration (FDA) says it has received complaints of the Mirena IUS causing pelvic inflammatory disease (PID) and other abdominal and pelvic pain, as well as headache, nausea, uterine bleeding, ovarian cysts, vaginitis, nervousness, depressed libido and depressed mood.

PID is an infection of the reproductive organs that can lead to serious consequences, including infertility, ectopic pregnancy (a pregnancy in the fallopian tube or elsewhere outside of the womb), abscess formation and chronic pelvic pain.