In our study, the presence of the HLA-DQA1*5 allele in both spouses increased the probability of high (>50%) overall HLA-DQA1 couple compatibility by a factor of 24.3 in the miscarriage group, whereas the corresponding odds were 10.5-fold higher for the IVF-ET failure group. Here, HLA-DQA1 is linked to spontaneous abortion.