Association between non-O blood type and early unexplained recurrent spontaneous abortion in women with and without inherited thrombophilia

We retrospectively evaluated the prevalence of non-O blood type – the most frequently inherited prothrombotic factor – and inherited thrombophilia (IT) in a group of women with recurrent spontaneous abortion (RSA). All consecutive women with a history of early unexplained RSA who underwent a screening for IT between December 2008 and December 2021 were considered for enrolment. A group of healthy, age-matched women with ≥1 normal pregnancy and no adverse pregnancy outcomes acted as controls. Two hundred and seventeen women were enrolled. The adjusted odds ratio (aOR) of RSA in non-O vs. O blood type was 1.37 (95% CI, 1.04-2.78), and in women with vs. without IT was 1.26 (95% CI, 1.08-3.61); aOR of RSA in women with non-O blood type and IT was 2.52 (95% CI, 1.12-5.47). We observed a significant association between non-O blood group or IT and RSA. The concomitant presence of non-O blood group and IT further increases RSA risk.