PGR and breast neoplasm: For ER-PR- breast tumors, similar risk associations to ER+PR+ breast tumors were observed with increasing menarcheal age (≥15 vs. ≤ 13 years ER-PR- HR: 0.84 [95% CI 0.69-1.03], Ptrend =0.17; ER+PR+ HR: 0.76 [95% CI 0.68-0.85], Ptrend <0.001; Phet = 0.48), and among parous women, with longer time between menarche and first full-term childbirth (≥10 vs. < 10 years ER-PR- HR: 1.15 [95% CI 0.99-1.34], Ptrend =0.09; ER+PR+ HR: 1.22 [95% CI 1.12-1.33], Ptrend <0.001; Phet = 0.52).