PELVIC ENDOMETRIOSIS - REPRODUCTIVE AND MENSTRUAL RISK-FACTORS AT DIFFERENT STAGES IN LOMBARDY, NORTHERN ITALY

Aim - To analyse the relationship between reproductive and menstrual f actors and different stages of pelvic endometriosis. Methods - Between 1987 and 1990 a case-control study of risk factors for pelvic endomet riosis was conducted. Cases comprised 376 women (median age 32 years) with pelvic endometriosis confirmed by laparoscopy or laparotomy admit ted to any one of three clinics in Lombardy, northern Italy. A total o f 129 (34.3%) of these women were at stage 1, 76 (20.2%) at stage 2, 9 6 (25.5%) at stage 3, and 75 (19.9%) at stage 4, according to the Amer ican Fertility Society revised classification of endometriosis. Contro ls comprised 522 women admitted to hospital for acute conditions. Resu lts - The risk of endometriosis decreased with increasing number of bi rths. The estimated odds ratios (OR) were similar in different stages of the disease: for example, compared with nulliparous women, the OR o f endometriosis at stage 1 was 0.1 in women who reported two or more b irths and the corresponding values were respectively 0.1, 0.2, and 0.2 for endometriosis at stages 2, 3, and 4. Cases reported fewer induced abortions than controls: the estimated ORs compared with no induced a bortion were 0.4, 0.5, 0.2, and 0.2 in women who reported one or more induced abortions for subsequent stages of endometriosis. Women with i rregular menstrual cycles were at less risk of the disease: compared w ith women who reported lifelong regular cycles the estimated ORs were 0.3, 0.5, 0.5, and 0.3 for disease stages 1-4 respectively. No consist ent association emerged between the ages at menarche and at first deli very and the risk of endometriosis. Conclusions - This analysis provid es further evidence that reproductive and menstrual factors are associ ated with the risk of endometriosis. The observation that early and la te stages of the disease share similar epidemiological characteristics suggests an epidemiological (and pathogenetic) continuum between vari ous stages of the disease.