Objective: Estrogen is known to promote glucose homeostasis, enhance insulin sensitivity, and maintain counterregulatory responses in recurrent hypoglycemia in women of reproductive age. Postmenopausal women with type 2 diabetes (T2DM) might be more vulnerable for severe hypoglycemia (SH) events. However, the relationship between reproductive factors and severe hypoglycemia occurrence in T2DM has not been evaluated. Methods: A total of 181,263 women with postmenopausal T2DM participating in a national health screening program from January 1 to December 31, 2009, were identified using the Korean National Health Insurance System database. Outcome data were obtained until December 31, 2018. Associations between reproductive factors and SH incidence were assessed using Cox proportional hazards models. Results: During the mean follow-up of 7.9 years, 11,279 (6.22%) postmenopausal women with T2DM experienced SH episodes. A longer reproductive span (RLS) (≥40 years) was associated with a lower SH risk than a shorter RLS (<30 years) (adjusted HR: 0.74; 95% CI: 15 0.69-0.8; P-for-trend <0.001) after multivariable adjustment. SH risk decreased with every 5-year increment of RLS (with <30 years as a reference; adjusted HR: 0.91 [95% CI, 0.86-0.95], P=0.0001 for 30-34 years group; adjusted HR: 0.80 [95% CI, 0.76- 0.85], P <0.001 for 35-39 years group; adjusted HR: 0.74 [95% CI, 0.68-0.81], P<0.001 for ≥40 years group). HRT was associated with a lower SH risk than that associated with HRT nonuse. Conclusion: Extended exposure to endogenous ovarian hormone during lifetime may decrease the number of SH events in women with T2DM after menopause