OBJECTIVE -To evaluate menstrual cycle histories among women with type 1 diabetes, their sisters, and unrelated control subjects without diabetes across all reproductive ages. RESEARCH DESIGN AND METHODS -Menstrual and reproductive histories were obtained by questionnaire from 143 women with type 1 diabetes, 186 sisters without diabetes, and 158 unrelated control subjects without diabetes participating in the Familial Autoimmune and Diabetes study. RESULTS -Women with type 1 diabetes had more

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... nstrual problems (long cycles, long menstruation, and heavy menstruation) before age 30 years than sisters and control subjects. These differences were all statistically significant, except for heavy menstruation at age Ͻ20 years. No differences were observed after age 30 years. Women with type 1 diabetes experienced later menarche, earlier natural menopause, fewer pregnancies, and more stillbirths than women without diabetes. Multiple regression analyses revealed that type 1 diabetes caused an approximate twofold increased risk of any menstrual problem before age 30 years. These were primarily related to long cycles and long menstruation in women aged Ͻ20 and 20 -29 years, as well as with heavy menstruation from 20 to 29 years. Oral contraceptives were protective for any menstrual problem and heavy menstruation from 30 to 39 years of age. With history of pregnancy from 20 to 40 years of age, any menstrual problem and long menstruation were more likely. CONCLUSIONS -The results suggest that type 1 diabetes is an independent risk factor for menstrual disturbances in young adults. Future studies may determine whether addressing menstrual disturbances improves quality of life and health for these women.