Use of oral contraceptives and uterine fibroids: results from a case-control study.

Abstract

To analyse the association between oral contraceptive use and the risk of uterine fibroids. We considered data collected in a case-control study on risk factors for uterine fibroids. We studied 843 women with uterine fibroids, whose clinical diagnosis dated back no more than two years. Controls were 1557 non-hysterectomised patients younger than 55 years admitted for acute, non-gynecological, non-hormonal, non-neoplastic conditions. A total of 254 cases (30.1%) and 360 controls (23.1%) reported ever using oral contraceptives: the odds ratio (OR) for ever vs never users was 1.1 (95% CI 0.8-1.3). The risk in current users was below unity when compared with never users (OR 0.3, 95% CI 0.2-0.6), while ex-users had a risk of fibroids comparable with never users (OR 1.1, 95% CI 0.9-1.4). The risk of uterine fibroids decreased with duration of oral contraceptive use: compared with never users, the estimated OR was 0.8 (95% CI 0.5-1.2) in ever users for four to six years and 0.5 (95% CI 0.3-0.9) for seven years or more (chi2 trend = 4.6, P = 0.03). Although the role of selection bias should be carefully evaluated, the present data suggest that uterine fibroids should not be considered a contra-indication for oral contraceptive use.