A weakly positive IgM in early pregnancy could be a cytomegalovirus infection, or it could be a false positive, which requires further analysis. 1. Cytomegalovirus infection or post-vaccination IgM may persist for several years at some point and does not indicate a new infection. 2. Patients with a recent history of rubella virus infection, human microvirus B19 infection, or infection with other pathogens may develop an alloantibody response to IgM resulting in a false-positive cytomegalovirus lgM antibody test result. 3. Patients with autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) may have false-positive results on the Macrocyte IgM antibody test due to the presence of rheumatoid factor in the body. 4. Infection with other viruses during pregnancy may trigger polyclonal B-cell activity, resulting in cytomegalovirus IgM expression. Therefore, it is recommended that patients with pure cytomegalovirus IgM positivity should go to the hospital in time for examination and treatment after the cause of the disease is clarified and followed by the doctor’s instructions.