Background: The etiology of uterine leiomyoma (or fibroids) is poorly understood. Sex steroid hormones and growth factors have been hypothesized to play a role in their development, and anthropometric characteristics may influence uterine leiomyoma risk.
Methods: We analyzed prospectively-collected data from the Nurses' Health Study II, a cohort of 116,609 female registered nurses age 25 to 42 years at baseline. Incidence of uterine leiomyoma and anthropometric characteristics were assessed every 2 years. We calculated hazard ratios and 95% confidence intervals adjusted for known and suspected risk factors for uterine leiomyoma.
Results: Uterine leiomyomas were associated with current body mass index, change in weight since age 18, and waist-to-hip ratio. However, there was little evidence of their association with body mass index at age 18, childhood or adolescent body size, or adult height.
Conclusion: Body mass and weight gain in adulthood may increase the risk of uterine leiomyoma, but body mass in early life does not.