IUD use and unexplained vaginal bleeding.

The Women's Health Study, a concurrent case-control study at 16 hospitals in 9 cities across the United States, examined the relationship between intrauterine contraceptive device (IUD) use and unexplained vaginal bleeding severe enough to require hospitalization. There were 545 eligible cases and 3453 controls. Analysis of all patients showed no association between IUD use and hospitalization for unexplained vaginal bleeding. When cases were analyzed separately with regard to prior episodes of vaginal bleeding, those patients with a history of vaginal bleeding had a decreased risk of hospitalization. Among cases, no significant differences between IUD users and nonusers were found in rates of anesthesia, blood transfusion, dilatation and curettage, or hysterectomy. The significant decreased risk between current IUD use (within 3 months before the study) and hospitalization for unexplained vaginal bleeding among women with a history of vaginal bleeding may reflect selective nonprescription for IUDs related to past episodes of vaginal bleeding.