Total of 356 women with various types of pregnancy disorders as well as their husbands were classified in four groups regarding the type of the disorder as follows: 1. Recurrent spontaneous abortions (RSA) of unknown etiology (N = 105) and RSA - primary aborters only (N = 84); 2. Blighted ovum (N = 80); 3. Rh immunization in pregnancy (N = 90); 4. ABO immunization in pregnancy (N = 47). Two groups of couples were used as controls: 1. Couples randomly taken from forensic medicine cases of paternity evaluation (N = 104); 2. Couples having two or more children with HLA immunization in pregnancy (N = 78). The couples from all groups were typed for red blood group antigens of ABO, Rhesus, MNSs, Kell, Duffy, Lewis, Kidd and P systems and also for HLA antigens. Significantly higher frequency of antigen HLA-A9 was found in women with RSA (corr. p = 0.0003) and in women with pregnancy disorders caused by Rh immunization (corr. p = 0.0136). In couples with RSA the degree of HLA compatibility was significant (p = 0.0048) and the reactivity of spouses in MLR was significantly decreased (p = 0.0001). Significantly, more low responders in MLR were also found among the women with RSA as compared to the controls (p = 0.0217). Two possible pathologic mechanisms may explain the association between HLA antigens and RSA: 1. immunological defects which are linked to HLA-D/DR region causing malfunction of immunosuppressive mechanisms during pregnancy; 2. endocrinological defect which is linked to HLA region as 21-OH hydroxylase deficiency gene.