Background: Maternal hemorrhage represents the most prevalent complication and primary cause of mortality during childbirth. Extensive studies have elucidated noteworthy correlations between ABO blood type and cardiovascular disease risk in both genders. Notably, individuals with blood type O exhibit a substantial variation in the formation of the platelet plug on vascular lesions, accompanied by a reduction in von Willebrand factor.

Main outcome measures: The primary aim of this study was to evaluate the potential association between blood type O and an elevated risk of post-partum hemorrhage. Secondary objectives were indications of a distinctive medical history via a modified questionnaire, hemostasis disorders, and the utilization of transfusions. The delivery route, post-partum hemoglobin, gestity, and maternal age will also be studied.

Results: Group O comprises the majority in our sample, with 1,475 patients. Among carriers and non-carriers within group O, no significant differences were observed in demographic data. However, in laboratory analyses, there was a notable difference (P-value<0.05) in pre-delivery hemoglobin, hematocrit, and aPTT between group O carriers and non-carriers. Nevertheless, no significant associations were identified between group O and abnormal bleeding (P=0.1655), aPTT (P=0.0741), HEMSTOP score ≥2 (P=0,9337), or transfusion use (P=0.8206).

Conclusion: No correlation was found between having blood type O and an elevated risk of post-partum hemorrhage, hemostasis disorders, abnormal medical history according to the standardized HEMSTOP questionnaire, or a higher frequency of transfusion. Therefore, the recommended clinical approach for patients with blood type O remains unchanged.