Characteristics related to the prevalence of minimal or mild endometriosis in infertile women. Canadian Collaborative Group on Endometriosis.

The objective of this case-control study is to identify factors associated with the prevalence of minimal or mild endometriosis among infertile women. Cases (N = 329) were women diagnosed by laparoscopy with minimal or mild endometriosis and without any other factors explaining their infertility. Controls (N = 262) were women in whom the infertility remained unexplained after a diagnostic laparoscopy. Selected characteristics were documented by means of a face-to-face interview before the laparoscopy. The prevalence of minimal or mild endometriosis was higher in women age 25 years or older, in those who reported menarche at the age of 13 years [prevalence odds ratio (POR) = 1.63; 95% confidence interval (CI) = 1.02-2.60] or older (POR = 1.73; 95% CI = 1.07-2.78), menstrual cycles of 27 days or less (POR = 1.63; 95% CI = 1.02-2.60), or caffeine intake of 300 mg per day or more (POR = 1.33; 95% CI = 0.91-1.94). The prevalence of minimal or mild endometriosis was inversely related to body mass index. Parous women were less likely to have endometriosis (POR = 0.61; 95% CI = 0.39-0.96) than were nulliparous women. Education, duration of infertility, and smoking status were not related to the presence of endometriosis.