The precautionary list of things to avoid during pregnancy is a long one. In this issue, researchers from the CDC remind us that there is another pathogen of which pregnant women should be wary.
As described by Stowell et al in this issue, congenital CMV is the most common congenital viral infection in the United States, and it is the most common nongenetic congenital cause of deafness. Most of the infants who will develop hearing loss due to congenital CMV infection appear entirely normal at birth, and in 20% of congenitally infected infants who will develop hearing loss, detection is delayed until well into childhood. Since there is no vaccine, what strategies can be used to detect infection in newborns so that periodic screening could identify hearing loss in time to avert speech delay and learning difficulties? So far, none of the screening strategies that have been proposed can be demonstrated to be sufficiently accurate to recommend in caring for pregnant women or newborns. There had been hope that detection of the virus in dried blood spots from newborns using polymerase chain reaction (PCR) technology would provide a cost-effective method for screening all newborns, but a recent large multicenter study by Boppana et al demonstrated that approximately 30% of infected infants would be missed using this technique.1
Until an effective vaccine can be developed to prevent CMV infection, we are left having to advise mothers to avoid CMV infection during pregnancy through washing their hands frequently and avoiding contact with urine and saliva. These practices are difficult even in the medical setting; they are nearly impossible with a young child in the home. Let's hope that vaccine comes soon.
1. Boppana SB, Ross SA, Novak Z, Shimamura M; for the National Institute on Deafness and Other Communication Disorders CMV and Hearing Multicenter Screening (CHIMES) Study. Dried blood spot real-time polymerase chain reaction assays to screen newborns for congenital cytomegalovirus infection. JAMA. 2010;303(14):1375-1382.