The association between carcinogenesis and subsequent bleeding is established. We investigated whether postpartum hemorrhage (PPH) may be a marker of clinically unrecognized cancer in women of reproductive age. In the full population, 51 224 women comprised the PPH cohort, and 536 016 women comprised the comparison cohort. In the primiparous population, 27 885 women comprised the PPH cohort, and 378 730 women comprised the comparison cohort. During the first year of the follow-up, the hazard ratio (HR) of any cancer adjusted for women’s morbidity, smoking, and parity, in the full and primiparous PPH populations was 1.13 (95% confidence interval [CI]: 0.89-1.44) and 0.97 (95%CI: 0.69-1.36), respectively. At 18 years of follow-up, HR of any cancer was 1.08 (95% CI: 1.02-1.16) for the full PPH population and 1.13 (95% CI: 1.04-1.24) for the primiparous PPH population.