Reproductive factors and risk of renal cell cancer: the Nurses' Health Study.

Few prospective studies have examined associations between reproductive factors and risk of renal cell cancer (RCC). The authors prospectively examined whether postmenopausal hormone (PMH) use, oral contraceptive use, parity, and other reproductive factors were associated with RCC risk among 118,219 US women in the Nurses' Health Study. A total of 247 RCC cases were confirmed between 1976 and 2004. Multivariate relative risks, adjusted for known risk factors, were calculated using Cox proportional hazards models. Compared with 1 or 2 childbirths, the multivariate relative risks were 1.75 (95% confidence interval (CI): 1.21, 2.53) for 4 childbirths and 1.50 (95% CI: 1.00, 2.23) for > or =5 childbirths (P(trend) = 0.02). Comparing an age at first birth of > or =28 years with an age at first birth of < or =22 years, the multivariate relative risk was 0.66 (95% CI: 0.43, 1.01; P(trend) = 0.01). Compared with 1-3 childbirths and an age at first birth of > or =26 years, the multivariate relative risk was 2.17 (95% CI: 1.49, 3.14) for > or =4 childbirths and an age at first birth of <26 years. No clear associations were observed for PMH use or duration, time since last PMH use, oral contraceptive use or duration, age at menarche, age at menopause, or history of hysterectomy or oophorectomy.