Evaluation of blood type as a potential risk factor for early postpartum hemorrhage

Objective Studies have demonstrated an association between ABO blood type and bleeding status. The aim of this analysis was to determine whether O blood type is associated with higher early postpartum hemorrhage (PPH) risk as compared to other blood types. Study design In this retrospective case-control study, data was gathered form 4,516 deliveries occurring at our institution between 2014 and 2016. Cases were categorized into one of two groups according to women’s major blood type (O or non-O), and thereafter according to minor blood type (RH positive or negative). The primary outcome was early PPH which was further stratified by clinical severity according to the decrement in hemoglobin concentration after delivery. Categorical variables were compared using the χ2 test while continuous variables were compared using the student's t-test. All data were further analyzed using a stepwise logistic regression model. Results 1,594 (35.3%) of 4,516 women included in this analysis had O blood type. Early PPH occurred in 44 women (2.7%) with O blood type and 65 women (2.22%) with other blood types. O blood type was not associated with an increased risk for early PPH (OR 1.24, 95% CI 0.84–1.82, P = 0.275). This lack of association remained unchanged after stratification by PPH severity. There was also no significant association between Rh blood type and the risk for early PPH (OR 0.97, 95% CI 0.44–1.4, P = 0.422). Conclusions In this cohort, O blood type was not associated with an increased risk for early PPH.