Epidemiology of endometriosis among parous women.

OBJECTIVE: To report the prevalence of endometriosis and its associated risk factors among multiparous women, and to determine the relationship between the location and depth of this disease and certain medical and behavioral characteristics.
METHODS: Over a 6-year period, 3384 multiparous women underwent laparoscopy for tubal sterilization. Endometriosis was detected in 126 patients (3.7%), who were consequently evaluated for severity of the disease. To conduct a case-control study, 504 patients with no evidence of endometriosis were randomly selected from a group of women who underwent sterilization. Information obtained through physical examination and a self-administered questionnaire was studied by multivariate logistic regression analysis.
RESULTS: Most endometriosis lesions were minimal. Factors associated with an increased risk for endometriosis included: advanced age (odds ratio [OR] 2.0, 95% confidence interval [CI] 1.1-3.7), Asian race (OR 8.6, 95% CI 1.4-20.1), long cycle length (OR 1.8, 95% CI 1.1-2.7), one live birth (OR 2.2, 95% CI 1.1-4.3), long duration of intrauterine device use (OR 3.0, 95% CI 1.1-8.1), and long duration of uninterrupted menstrual cycles (OR 2.9, 95% CI 1.3-6.4). Present oral contraceptive use was protective for disease (OR 0.5, 95% CI 0.2-0.9). The role of these factors varied among different disease locations (ovary, uterus and tubes, posterior broad ligaments and cul-de-sac), and depth (superficial or deep).
CONCLUSIONS: The prevalence of endometriosis is relatively low among multiparous women, and certain menstrual and reproductive characteristics are associated with its development. Furthermore, the relationship between various factors and endometriosis appears to be site and depth specific. Our findings suggest that asymptomatic endometriosis may be clinically important.