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

Abstract

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.

PIP: The 95,061 US women enrolled in the 1989 cohort of the Nurses' Health Study II were queried, in the 1993 questionnaire, about any recent history of uterine leiomyomata. At study enrollment (at ages 25-42 years), all women were premenopausal and had intact uteri with no history of diagnosed uterine leiomyomata or cancer. During 326,116 woman-years of follow-up, 3006 new 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 significantly positively associated with a history of infertility and years since last birth. The only significant oral contraceptive (OC)-related association was an elevated risk among women who first used OCs at ages 13-16 years compared with OC never-users. The excess risk persisted after controls for histories of menstrual cycle irregularity in high school and severe teenage acne--factors that may have led to the prescription of OCs in early adolescence. The increased risk among women with an early menarche and decreased risks among parous and high-parity women support the hypothesis that myometrial responses to estrogens may be important in the etiology of uterine leiomyomata. The role of exogenous hormones resulting from OC use remains unclear.