Reproductive factors and risk of uterine fibroids

We analyzed the relation between reproductive history and risk of uterine fibroids using data from a case-control study. Cases were 621 women with histologically confirmed diagnosis of uterine fibroids. Controls were 1,051 nonhysterectomized patients. Compared with nulliparae, parous women had a relative risk (RR) of fibroids of 0.5 [95% confidence interval (CI) = 0.4-0.6], and the risk declined with number of births. The risk of fibroids also decreased with number of induced abortions (RR = 0.8 and 0.6 for women reporting one or two or more abortions, respectively). A total of 24 cases (3.9%) and 19 controls (1.8%) reported a history of infertility (RR = 2.0; 95% Cl = 1.1-3.7).