Cytomegalovirus (CMV) is a group of DNA viruses 110 millimeters in diameter. In the past, rubella virus was thought to be the most dangerous to the fetus. In recent years, virological studies have demonstrated that because cytomegalovirus infection is widespread in the population, infection in pregnant women can be transmitted to the fetus, causing fetal infections and malformations. Therefore, CMV is currently considered to be one of the most important pathogens of congenital viral infections, and its risk to the fetus is even greater than that of rubella virus. Primary infections, i.e. initial infections, are not harmful to the pregnant women themselves, most of them have no obvious symptoms and can only be diagnosed by serology. However, it can produce viremia and the virus is transmitted to the fetus through the placenta. CMV is a latent virus that stops after months or years of detoxification in patients with primary infection, and the virus is latent in the body. When pregnant or immunocompromised, the latent virus is activated and is called a recurrent infection. The positive rate of anti-CMV-IG antibodies among women in China is about 98%, which means that most women in China have been infected with CMV during childhood and their bodies have produced antibodies, but CMV is different from other viruses in that antibodies in the mother’s body cannot protect the fetus from infection, so a pregnant woman with recurrent infection may still transmit CMV to her baby. There are three ways to transmit CMV from mother to fetus: 1. Intrauterine infection When the mother has a primary infection, the virus can be transmitted to the fetus through the placenta. Virus isolated in the urine of a newborn within 1 week of birth can prove to be a congenital infection. The rate of congenital CMV infection in China is 0.5 to 0.9%. 2, cervical infection Endocrine changes during pregnancy activates the latent virus in pregnant women, which increases the CMV infection in the cervix of pregnant women and infects the fetus through the birth canal during delivery. 3, breast milk infection Newborn babies can be infected through breastfeeding. The rate of CMV positivity in breast milk in China is 13%. Infection through the cervix or breast milk is also called perinatal infection. These infants are urine negative within a week of birth and start to detoxify after 3 to 4 weeks. Most infants with perinatal infections are asymptomatic or have mild symptoms. The degree of fetal infection and involvement is related to the gestational period of the pregnant woman at the time of infection. Intrauterine infection in early maternal gestation, when the fetus is severely infected and the newborn has giant cell inclusion body disease. In late maternal gestation, the fetus is well developed and therefore less involved, and the newborn is born with milder symptoms or only viral urine. Infected infants have prolonged intermittent detoxification for up to 3 to 5 years or more. What are the risks of CMV infection for infants? The common symptoms of congenital CMV infection called cytomegalic inclusion body disease (CID) are jaundice, hepatosplenomegaly, microcephaly, petechiae, mental retardation, motor dysfunction, deafness, chorioretinitis, pneumonia, congenital heart disease and various other malformations in newborns after birth, and also cause premature birth or miscarriage of the fetus. In severe cases, newborns are born with respiratory distress and seizures, and die within days to weeks. It has been observed that the incidence of infant hepatitis symptoms such as jaundice, hepatosplenomegaly, and elevated transaminases is higher in CID cases. In most infants, the jaundice subsides and the disease recovers after a few weeks or months. In a few infants, the jaundice worsens, the stools become white, symptoms of biliary atresia develop, and eventually death occurs from biliary stasis cirrhosis. Cytomegalovirus-induced microcephaly is often associated with severe mental retardation and sometimes combined with ocular defects such as small eyeballs, small eye slits, small corneas, strabismus, cataracts, or optic nerve atrophy. In China, about 5-10% of infants with giant cell inclusion disease have the above-mentioned typical symptoms, and 90-95% have asymptomatic infection, only urinary excretion, called quiescent infection or latent infection. About 10% of these asymptomatic infected children gradually develop symptoms of neurological damage such as deafness, mental retardation, and visual impairment several years later. The laboratory diagnosis of congenital infection relies mainly on virus isolation and serological examination. The diagnosis can be confirmed by the isolation of CMV in the urine or saliva of the child and by positive anti-CMV-IM antibodies in the blood or umbilical cord blood of the child. How can cytomegalovirus infection be prevented so that eugenics can be achieved? Congenital CMV infection is very dangerous for children, and there are no effective antiviral drugs or other specific treatments available, so the focus should be on prevention. Virological testing of pregnant women, especially for those with a history of early colds or teratogenic births, is more important. When anti-CMV-IM antibodies are detected in the blood of a pregnant woman, or when anti-CMV-IG antibodies are found to be positive, it means that CMV has been isolated in the amniotic fluid of the pregnant woman indicating intrauterine infection. Both of these cases can be considered for termination of pregnancy, which can reduce the birth of severely infected children and malformed children for eugenic purposes.