Risk factors for seromucinous benign ovarian cysts in northern Italy.

STUDY OBJECTIVE To analyse risk factors for seromucinous benign ovarian cysts. DESIGN Between 1984 and 1994 a case-control study was carried out. Cases were 225 women aged less than 65 year with a histologically confirmed diagnosis of benign seromucinous ovarian cysts admitted to a network of obstetrics and gynaecology departments in Milan. Controls were a random sample of 450 women admitted for acute conditions that were not gynaecological, hormonal or neoplastic. They were interviewed within the framework of a case-control study of female genital neoplasms. SETTING Network of hospitals in the greater Milan area, Italy. MAIN RESULTS The risk of seromucinous benign ovarian cysts was higher in more educated women than in women with fewer than seven years of schooling. The odds ratios (OR) for seromucinous ovarian cysts were 1.3 and 1.4 respectively in women reporting 7-11 and > or = 12 years of schooling, and the trend in risk was statistically significant (chi(2)1 trend 5.20, p < 0.05). There was no clear relationship between the risk of seromucinous ovarian cysts and marital status, age at first marriage, oral contraceptive use, smoking or body mass index. In comparison with women reporting menstrual cycles lasting < 28 days, the risks of seromucinous cysts were 1.6, 2.6, and 2.5 respectively in women reporting cycles lasting 28-30, > or = 31 days, or with totally irregular ones. Among ever married women, nine cases and two controls reported difficulty in conception, and the corresponding OR for seromucinous cysts was 17.7 (95% confidence interval 4.2, 83.8). CONCLUSIONS The risk of seromucinous benign ovarian tumours is greater in more educated women and in women with a history of infertility and with long or irregular menstrual cycles.