Leuven, Belgium — in a Belgian study conducted at the Laboratory of Clinical Virology, Rega Institute for Medical Research, University of Leuven, four in five children of mothers infected in early pregnancy with a herpes virus were found to suffer from hearing damage, says a statement from the Journal of Clinical Microbiology. The mothers were among the up to 4% of all pregnant women who become infected with the cytomegalovirus.

Cytomegalovirus is found in more than half of the total population. The virus rarely causes symptoms in healthy adults. But when transmitted from mother to child in the first 3months of pregnancy, it may cause problems.

The study, whose results were published in the Journal of Clinical Microbiology, found that four in five of these children developed sensorineural hearing loss because their mothers were infected by the virus in the first 3 months of pregnancy. In a fetus, the ears develop mainly between weeks 3 to 10 of a pregnancy. This is likely to make the ears particularly sensitive to viral infections at this stage.

From the article’s abstract:

"Since auditory disability causes serious problems in the development of speech and in the total development of a child, it is crucial to diagnose possible hearing impairment as soon as possible after birth. This study evaluates the neonatal hearing screening program in Flanders, Belgium. The auditory ability of 118,438 babies was tested using the automated auditory brainstem response (AABR). We selected 194 babies with indicative hearing impairment and 332 matched controls to investigate the association between the presence of human cytomegalovirus (HCMV) in urine samples and sensorineural hearing loss (SNHL), and to compare the sensibility and specificity of a cell culture assay and a quantitative PCR detection method. Our results indicate that significantly more babies with confirmed hearing impairment were HCMV positive after birth. Even more, based on the results of our study, babies with HCMV viral loads above 4.5 log copies/mL urine, seem to be 1.4 times more likely to have confirmed hearing impairment. Our follow-up study suggests that the hearing impairment of children infected with HCMV after birth, is less likely to improve compared to HCMV negative infants. Our results confirm that the presence of HCMV before or shortly after birth influences the outcome of hearing impairment."

When the viral infection occurs later in pregnancy, the risk to the hearing of the child is smaller. Just one child in 12 born to mothers infected during the second trimester of pregnancy was found to suffer from hearing loss. No hearing loss was found in children whose mothers were infected in the third trimester of pregnancy.

According to the Centers for Disease Control (CDC), between 1% to 4% of pregnant women are infected with cytomegalovirus.

Cytomegalovirus spreads from person to person through body fluids. Frequent hand washing with soap, particularly following potential contact with the body fluids of others, can reduce the risk of infection and is recommended for all pregnant women by the CDC.

SOURCE: Journal of Clinical Microbiology