Premature ovarian failure: frequency and risk factors among women attending a network of menopause clinics in Italy.

OBJECTIVE To determine the frequency and causes of preterm ovarian failure (menopause before 40 years of age) and early menopause (menopause between 40 and 45 years). DESIGN Cross sectional study. SETTING Menopause clinics in Italy. POPULATION Women attending menopause clinics in Italy. METHODS Between 1997 and 1999 we conducted a large cross sectional study on the characteristics of women around menopause attending a network of first-level outpatient menopause clinics in Italy for general counselling about menopause or treatment of menopausal symptoms. Eligible for the study were all women aged 45-75 years consecutively observed for the first time at the participating centres on randomly selected days during the study period. MAIN OUTCOME MEASURE Factors associated with preterm ovarian failure. RESULTS Out of 15,253 women aged 55 years or more with spontaneous menopause who entered the study, 269 (1.8%) reported preterm ovarian failure, and 1085 (7.1%) reported spontaneous menopause at age 40-45 years. The risk of preterm ovarian failure and of early menopause was higher in women reporting lifelong irregular menstrual cycles: in comparison with women reporting menopause at age > or =45 years, the OR (irregular vs regular menstrual cycles) of preterm ovarian failure was 1.3 (95% CI 1.0-1.7) and of early menopause of 1.2 (95% CI 1.0-1.5). Parous women reported less frequently preterm ovarian failure (chi(2) trend P < 0.05) and early menopause (OR 0.8, 95% CI 0.7-1.0). No significant association emerged between risk of preterm ovarian failure or menopause at age 40 to <45 and education, age at menarche, oral contraceptive use and smoking habits. CONCLUSION Nulliparity and lifelong irregular menstrual cycles are associated with an increased risk of preterm ovarian failure.