A prospective study of reproductive factors and oral contraceptive use in relation to the risk of uterine leiomyomata

Objective: To investigate the risk of uterine leiomyomata in relation to reproductive factors and oral contraceptive use. Design: A prospective study. Setting: A cohort of female registered nurses from 14 states in the United States who completed mailed questionnaires in 1989, 1991, and 1993. Patient(s): Premenopausal nurses (n = 95,061) aged 25-42 years with intact uteri and no history of diagnosed uterine leiomyomata or cancer in 1989. Intervention(s): None. Main Outcome Measure(s): Incidence of self-reported uterine leiomyomata confirmed by ultrasound or hysterectomy. In a sample of 243 cases, 93% of the self-reported diagnoses were confirmed in the medical record. Result(s): During 326,116 person-years of follow-up, 3,006 cases of uterine leiomyomata, confirmed by ultrasound or hysterectomy, were reported. After adjustment for other risk factors, the risk of uterine leiomyomata was significantly inversely associated with age at menarche, parity, and age at first birth, and positively associated with a history of infertility and years since last birth. The only notable association with any aspect of oral contraceptive use was a significantly elevated risk among women who first used oral contraceptives at ages 13-16 years compared with those who had never used oral contraceptives. Conclusion(s): Reproductive factors and oral contraceptive use at a young age influence the risk of uterine leiomyomata among premenopausal women. (Fertil Steril(R) 1998;70:432-9. (C)1998 by American Society for Reproductive Medicine.).