Postdoctoral Scientist, Virology Research Laboratory at Faculty of Medicine, UNSW.
Cytomegalovirus (CMV) is a virus transmitted from person to person via body fluids like urine or saliva. For people with a healthy immune system, CMV is likely to cause no more than a temporary fever or headache. But when a pregnant woman is infected, the results can be far more serious.
While a pregnant woman herself may not feel sick, the virus can cross the placenta to infect her unborn child and cause permanent disability, including hearing loss and intellectual disability.
In Australia, nearly 2,000 babies are born infected with CMV every year. About 380 of these are born with permanent disabilities, including deafness, blindness and intellectual disability.
In developed countries, about one in five babies born with CMV will have permanent disabilities. This makes CMV the leading infectious cause of disability in newborns in the developed world.
Researchers don’t know the exact mechanism by which CMV can infect the developing baby. But they suspect the virus in the pregnant women’s blood first infects the cells of the placenta, where it multiplies and then enters the baby’s circulation via the placenta’s blood vessels.
Researchers also do not fully understand how CMV then causes hearing loss or intellectual disability. But CMV is thought to directly infect and damage a part of the inner ear. CMV also seems to infect neural stem cells, which are the building blocks of the developing brain. This infection may stop these brain cells from dividing and multiplying, which could affect the size of the baby’s brain and how it matures. CMV infection in the placenta may also prevent the placenta from developing properly. This could reduce the oxygen and nutrients to the baby, which can lead to brain abnormalities.
Most pregnant women are not aware
Most pregnant women are unaware of CMV and the simple measures they can take to reduce the chance of contracting this virus.
Studies in Canada, the US, France, Switzerland, the Netherlands, Japan, and Singapore report 61-87% of pregnant women have not heard of the virus. We predict similar rates in Australian pregnant women, although studies to confirm this have not been done yet.
There are no CMV awareness campaigns to provide pregnant women with much needed information about how to protect their baby from CMV, except those run by community organisations, such as in the US, the UK and Australia.
This means, without knowing, many pregnant women are unintentionally putting their baby at risk of CMV infection.