Blood group 0: A novel risk factor for postpartum hemorrhage?

Background:

Blood group 0 is known to be associated with lower levels of active von Willebrand factor (VWF) and with increased incidence of bleeding complications. The influence of maternal blood group 0 on postpartum hemorrhage (PPH) was assessed by a few studies, however without adjustment for important obstetric risk factors for PPH.

Aim of this study was to investigate whether women with blood group 0 exhibit a higher risk for hemorrhage after delivery in consideration of established risk factors for increased postpartum blood loss.

Methods:

1487 patients were prospectively included into this study. Blood loss was assessed by estimated blood loss (in ml) and calculated drop of hemoglobin (Δ hemoglobin). Associations of blood loss with risk factors (such as blood group 0, cervical tears, morbidly adherent placenta, placenta praevia and uterine atony amongst others) was assessed with Pearson correlation or t-test as appropriate. Significant variables were entered into a stepwise multivariate regression analysis.

Results:

Women with blood group 0 showed a significantly higher blood loss (43 mL) when compared to women with blood group non-0. The association remained significant after multivariate regression analysis (p= 0.019).

Conclusions:

This is the first study reporting significantly increased blood loss following delivery in women with blood group 0 after adjustment for major PPH risk factors. Albeit having a statistically significant, but clinically minor effect on absolute blood loss, blood group 0 carriers may aggravate bleeding due to the presence of additional obstetric risk factors for PPH.