Cytomegalovirus (CMV)

Cytomegalovirus (CMV) is a member of the "herpes" family of viruses along with the viruses responsible for glandular fever and chicken pox. Following a first "primary" infection, the virus is able to rest dormant in the body before a "reactivation" that can occur at any time including during pregnancy. In Europe around half of pregnant women have not had CMV infection before and therefore are at risk of a primary infection during their pregnancy. CMV is present in all bodily fluids. Around 40% of children attending crèches excrete the virus in their urine and saliva. Therefore pregnant women should be careful when in contact with young children (hand washing, avoid sharing utensils, etc ...). They should also be careful when near anyone with signs of a cold as this could be due to CMV. The risk of transmission of the virus from mother to the baby is around 40% for a primary infection and less than 2% for a reactivation. Around 90% of babies infected during pregnancy are asymptomatic at birth although around 10-15% will develop a problem in the first few years of life- most frequently hearing impairment. Therefore all such babies should be followed up be a paediatrician. Of the 10% that are symptomatic at birth, half are affected mildly but half are affected severely. In order to identify babies that are affected by CMV, you may be offered monthly blood tests if you have never had the infection before. Following infection specific antibodies will appear which will instruct the obstetrician to perform regular ultrasound scans and occasionally an amniocentesis to test for the presence of infection in the amniotic fluid. If no signs are evident on ultrasound scan then the prognosis is generally good but if signs are present then the parents can be informed of the likely outcome and consider their options for the pregnancy. Unfortunately there is at present no vaccine and no treatment for CMV.