ObjectiveTo compare the safety and regression rates of conservative treatments for complex atypical hyperplasia (CAH) between pre- and postmenopausal women.MethodsHistorical cohort study of pre- and postmenopausal women with CAH managed conservatively at one center (Royal Women’s Hospital, Melbourne, Australia) between September 1999 to June 2012.ResultsOf the 153 women with CAH, 92 (60%) underwent hysterectomy and the remaining 61 were managed conservatively with oral or intrauterine progestogen: 42 were premenopausal and 19 were postmenopausal. Within 12 months, 32 (76%) premenopausal women demonstrated regression of CAH and none developed endometrial cancer. In contrast, only 4 (21%) postmenopausal women showed disease regression and 4 (21%) progressed to endometrial cancer. Over a median of 24 months, 3 premenopausal women relapsed with CAH and 2 developed endometrial cancer. Four premenopausal women had successful pregnancies.ConclusionConservative treatment with progestogen in premenopausal women with CAH leads to high regression rates within the first 12 months. In contrast, postmenopausal women have high rates of ongoing disease and cancer progression and conservative therapy should be avoided.