Introduction: The common perception that this treatment has no serious side effects is probably influenced by this flawed evidence. In this large population-based study, our goals were to determine whether there was an independent relationship between the amount of oxytocin exposed during labor and the risk of developing severe PPH and to determine whether the prophylactic use of oxytocin after delivery affected this relationship. Material and Methods: women who had straightforward pregnancies and delivered term singletons vaginally. Cases were 1483 women with severe PPH, which was indicated by peripartum hemoglobin changes of less than 4 g/dl or the requirement for blood transfusions. 90 women from a randomly selected group of expectant mothers without PPH served as the controls. Using two-level multivariable logistic regression modeling, the independent relationship between the oxytocin level during labor and the risk of developing severe PPH was examined and quantified with ORs. Results: After adjusting for all possible confounders, oxytocin exposure during labor was linked to a higher risk of severe PPH when prophylactic oxytocin was not given after delivery. With more oxytocin injected, the association became stronger. The risk of severe PPH was approximately three times higher for total doses between 2 and 4 IU and six times higher for total doses over 4 IU. Conclusion: A separate risk factor for severe PPH appears to be oxytocin during labor. Our findings add to the body of evidence highlighting the need for precautions to reduce maternal complications when oxytocin is used to speed up labor, including strict indications, the use of the lowest effective dose, and careful efficacy evaluation.