ESR1 and breast carcinoma: Furthermore, while a history of gestational diabetes mellitus (GDM) alone is not associated with breast cancer in the Sister Study (HR = 1.10, 95% CI = 0.88–1.36), having two or more GDM pregnancies increased breast cancer risk in future, particularly for estrogen receptor-positive breast cancer (HR = 1.81, 95% CI = 1.10–2.98) [39], align with current study result (P < 0.0001).