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5430509 
Journal Article 
In utero exposures and the incidence of endometriosis 
Missmer, SA; Hankinson, SE; Spiegelman, D; Barbieri, RL; Hunter, DJ 
2003 
Yes 
American Journal of Epidemiology
ISSN: 0002-9262
EISSN: 1476-6256 
157 
English 
Breast cancer, testicular cancer, cardiovascular disease, and diabetes have been associated with birthweight and other proxies of in utero exposures. To investigate the relation between the fetal environment and endometriosis, a prevalent and often debilitating gynecologic disorder defined by the presence of endometrial tissue outside of the uterus, we analyzed 10 years of prospective data from the Nurses' Health Study II that began in 1989. During 726,759 woman-years of follow-up, 1706 cases of laparoscopically-confirmed endometriosis were reported among women with no history of infertility. In cox proportional hazards models adjusted for parity, race, and body mass index at age 18 (BMI18), we observed a linear decrease in the incidence rate with increasing birthweight (rate ratio (RR) = 0.7 for birthweight and gt; 8.4 pounds versus and lt; 5.5 pounds, 95% confidence interval (CI) = 0.5, 1.0, p-value, test for trend = 0.01). In addition, women who were born as one of a multiple gestation (i.e. twins or greater number) were at increased risk (RR = 1.7, CI = 1.2, 2.5). Neither premature delivery nor having been breastfed were associated with the incidence of endometriosis. None of these effect estimates were modified by infertility status at the time of endometriosis diagnosis. We conclude that the fetal environment, potentially via the magnitude of in utero exposure to circulating estrogens, is associated with the rate of laparoscopically-confirmed endometriosis within this cohort of US registered nurses.