Objective: To perform serological identification and molecular analysis of four samples with antibodies against high-frequency antigens, and to track the condition of newborns after delivery. Methods: Blood group serological tests were conducted using tube method, and unexpected antibody screening and identification were performed using polybrene and human globulin card. Gene haplotype analysis of blood group system was performed using PacBio third-generation sequencing. The DNA mutations were confirmed through Sanger sequencing. Results: Four samples showed normal blood types in common blood type systems. However, they were positive in all unexpected antibody screening and identification, with negative direct antiglobulin tests results. Third-generation sequencing revealed 3 cases of c.376C>T homozygous mutation and 1 case of c.421C>A homozygous mutation in the ABCG2 gene. Three pregnant women gave birth to four children, all of whom developed hyperbilirubinemia, accompanied by decreased red blood cell count and normal or low hemoglobin concentration. Conclusion: Four samples were obtained from individuals with the rare Jr(a-) blood group. Immunization during pregnancy led to the production of anti-Jr antibody, which may contribute to hyperbilirubinemia in newborns.