A new study by researchers in Belgium has found that children have a higher risk of hearing loss due to congenital cytomegalovirus (CMV) infection if their mother was infected with the virus during the first trimester of pregnancy rather than in the later stages.
CMV, a type of herpesvirus, has infected nearly 50 percent of the population. And although the virus rarely causes symptoms in those with healthy immune systems, it can cause problems when passed from a mother to her fetus during pregnancy.
Congenital CMV infection is the most common viral infection affecting the fetus, wrote Dr. Ina Foulon and colleagues from Universitair Ziekenhuis in Brussels, Belgium, in a report about their study.
The researchers had found in a previous study that children with congenital CMV carried a 22 percent risk of developing sensorineural hearing loss –the type caused by nerve damage.
In the current study, the scientists looked at the link between CMV infection occurring at different stages of pregnancy and sensorineural hearing loss in 34 children with congenital CMV infection.
During the course of the study, 5 children were lost to follow-up and 1 died, leaving 28 remaining children. Of these, sensorineural hearing loss occurred in 80 percent of the children born to mothers who had a CMV infection during their first trimester of pregnancy, and 8 percent of those born to mothers with a CMV infection during the second trimester.
None of the children born to mothers with CMV infections during their third trimester of pregnancy experienced sensorineural hearing loss. Progression of sensorineural hearing loss was seen in 2 children born after a maternal CMV infection during the first trimester.
The researchers explain that the vulnerability of hearing to early CMV infection in the womb may be explained by the embryological development of the ear, which occurs in large part between the 3rd and 10th week of gestation.
The study was published in the December 2008 journal Pediatrics.
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