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 prospect ive study. Setting: A cohort of female registered nurses from 14 state s in the United States who completed mailed questionnaires in 1989, 19 91, and 1993. Patient(s): Premenopausal nurses (n = 95,061) aged 25-42 years with intact uteri and no history of diagnosed uterine leiomyoma ta 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 d iagnoses were confirmed in the medical record. Result(s): During 326,1 16 person-years of follow-up, 3,006 cases of uterine leiomyomata, conf irmed by ultrasound or hysterectomy, were reported. After adjustment f or other risk factors, the risk of uterine leiomyomata was significant ly inversely associated with age at menarche, parity, and age at first birth, and positively associated with a history of infertility and ye ars since last birth. The only notable association with any aspect of oral contraceptive use was a significantly elevated risk among women w ho first used oral contraceptives at ages 13-16 years compared with th ose who had never used oral contraceptives. Conclusion(s): Reproductiv e factors and oral contraceptive use at a young age influence the risk of uterine leiomyomata among premenopausal women. (Fertil Steril(R) 1 998;70:432-9. (C)1998 by American Society for Reproductive Medicine.).