Studies have demonstrated that mRNA expression of PD‐L1, but not PD‐1, is significantly decreased in decidual tissues from cases of recurrent miscarriage compared to controls.31 Similarly, Wu et al32 found that women with recurrent spontaneous abortions (defined as 3 or more pregnancy losses) had lower levels of galectin‐9 in peripheral blood compared to the normal pregnancy group. This evidence concerns the gene CD274 and spontaneous abortion.