CD274 and metastatic malignant neoplasm: Because of lacking a (68) adequate and well-controlled studies and based on the findings in mouse models, where blockade of the PD-1/PD-L1 pathway resulted in the adverse effect on pregnancy, checkpoint inhibitors are relatively contraindicated for the treatment of metastatic cancer in pregnant women requiring an individualized decision in each case (22, 97, 100, 111, 112).