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The authors conducted a population-based case-control study of 410 women residing in three counties in western Washington State who were aged 18–64 years when diagnosed with papillary thyroid cancer in 1988–1994 and 574 controls to assess the effects of pregnancy history and other aspects of reproductive life on risk of this disease. Among women aged 45–64, the authors observed no associations with number of live births, age at first live birth, or age at last live birth. Risk was somewhat increased in women <45 years who had given birth within the previous 5 years; this association was most evident among women who reported that cancer symptoms had led to diagnosis. Among women who had given birth within the last 5 years, risk was greatest among those with two or more births during that time period (relative risk (RR) = 4.2, 95% confidence interval (Cl): 2.0, 8.9, relative to parous women whose last birth was >5 years before the reference date). Risk of thyroid cancer was also associated with lactation during the previous 5 years (e.g., RR = 2.9, 95% Cl: 1.5, 5.5, among parous women who had breastfed £12 months, vs. 0–1 months, during that interval). Our results suggest that thyroid stimulation during both pregnancy and lactation may result in a transient increase in risk of papillary thyroid cancer. Am J Epidemiol 2000;151:765–72. [ABSTRACT FROM PUBLISHER]

The authors conducted a population-based, case-control study among women aged 35–54 years to assess the influence of infertility and use of ovulation-inducing drugs on ovarian cancer risk. The study was conducted from 1994 to 1998 in three regions (metropolitan Atlanta, Georgia, Detroit, Michigan, and Seattle, Washington) and included 378 cases and 1,637 controls. Data were obtained through in-person interviews, and analysis was conducted using unconditional logistic regression. Among parous women, the authors observed no association of cancer risk with a history of infertility, medical evaluation for infertility, specific types of infertility, or use of ovulation-inducing drugs. Among nulliparous women, risk was increased among women with a history of infertility (odds ratio = 1.6, 95% confidence interval: 1.0, 2.6), particularly when infertility first became manifest relatively late in reproductive life (for first infertility at ≥30 years of age: odds ratio = 2.2, 95% confidence interval: 1.1, 4.5); risk was not associated with medical evaluation for infertility, specific types of infertility, or use of ovulation-inducing drugs. Findings were similar when borderline and invasive epithelial tumors were considered separately. While the results of this study support the hypothesis that a subset of nulliparous women who experience infertility may be at increased risk of ovarian cancer, the reasons for this increase in risk remain unclear. [ABSTRACT FROM AUTHOR]