ABO blood group and fertility: a single-centre study.

The ABO blood group exerts a profound influence on haemostasis, documented by the close relationship between ABO blood type and von Willebrand factor (VWF), and hence factor VIII (FVIII), plasma levels1. Individuals with blood group O have approximately 25% lower VWF plasma levels compared with those with non-O blood groups2. Among people with non-O groups, AB individuals have the highest VWF and FVIII levels, followed by group B and then group A2. Several epidemiological studies and systematic reviews have analysed the clinical consequences of this phenomenon, especially regarding the risk of developing venous and arterial thromboses3–5. However, beside the association with various pathological processes, it would also be interesting to know whether the non-O blood type-related enhanced clot formation, documented by thrombin generation tests6, is also able to influence some physiological processes linked to haemostasis7. A possible relationship between ABO blood group antigens in women and uterine embryo implantation is particularly intriguing. With the aim of investigating the effect of ABO blood group system on female fertility, we conducted a single-centre study evaluating the correlation of ABO blood group system in female blood donors with and without children and in pregnant women.