If a pregnant mother receives such a test result in the middle and late stages of pregnancy and keeps asking, “Doctor, will a positive virus affect my baby? What should I do?” . This is really a difficult question for doctors to explain. If cytomegalovirus infection occurs early in pregnancy, the effects on the fetus are much more serious than if it occurs in the middle or late stages of pregnancy. Cytomegalovirus infection can cause not only abnormal fetal development, but also abnormal fetal neurological development, including deafness. Some infected fetuses may show problems on ultrasound, such as fetal abdominal calcification, hydrocephalus or widening of the lateral ventricles, but there are still some effects that cannot be diagnosed before birth and require a definitive diagnosis after the child is born, or even some time after birth. Many people do not feel anything after the initial infection, and only a few will have flu-like symptoms such as fever and muscle pain. In general, CMV antibodies IgM can be detected in our body about 2-3 weeks after cytomegalovirus infection. If IgM antibodies are positive, it indicates an acute infection, but it will disappear within 30-60 days and the antibodies in our body will change again to IgG, which represents a previously occurred infection. Therefore a positive IgG cytomegalovirus antibody found during mid- to late-pregnancy tests often does not allow to deduce exactly when the infection occurred, in early pregnancy? Or did it occur prior to pregnancy? If it occurred relatively long before pregnancy, there is no need to worry about any impact on the child, unless it is a re-infection, and another recurrent infection would have even less impact on the child. In fact, there is a lot of uncertainty in the two antibody tests for cytomegalovirus: a change from negative to positive IgG, or a significant increase of more than 4-fold can diagnose cytomegalovirus infection. A positive cytomegalovirus IgM can be helpful in diagnosing the initial infection, but there are special cases where it cannot be detected. Another point is that even if the mother is infected, it does not mean that the amniotic cavity is infected (the “house” where the child lives until birth); even if the amniotic cavity of the “house” is infected, it does not mean that the fetus is infected; even if the fetus is infected, in many cases it is not detected during pregnancy. Even if the fetus is infected, in many cases it is not detected during pregnancy, and in some cases it can only be detected after the birth of the child; and in order to check whether the child is infected or not, the doctor will recommend amniocentesis to draw amniotic fluid for examination, and will the amniocentesis process cause the fetus to become infected after the procedure itself if it is not infected? It is impossible to have a definite answer to this question. In addition, due to the immaturity of the fetal immune system, antibodies to viruses cannot be detected in the fetus before the 21st week of pregnancy through amniotic fluid. Therefore, congenital CMV infection cannot be detected by current medical conditions. Therefore, the current medical opinion in foreign countries (including developed countries) and China does not recommend routine screening of all pregnant women for the virus, because if antibodies are detected, the doctor cannot make a more accurate diagnosis, cannot provide an effective treatment plan, and is unable to make an accurate prognosis assessment, not to mention the possibility of false antibody positivity, which adds to the psychological burden of the pregnant mother. However, if there is a high suspicion of viral infection during pregnancy, it is still necessary to be tested. Currently our domestic guidelines for preconception and pregnancy care only recommend that viral screening can be done before pregnancy for eugenic needs and to prepare for pregnancy and the timing of preparation. If there are no special circumstances, routine screening is not recommended during pregnancy.