The drug, called hyperimmune globulin, cut rates of mother-to-child transmission of cytomegalovirus (CMV) to just 3 percent of babies born to women infected with the virus.
In contrast, 50 percent of infected mothers who did not receive the treatment passed on the potentially harmful pathogen to their newborn.
"Hyperimmune globulin was effective in treating and preventing mothers from transmitting the infection," said study co-author Dr. Stuart Adler, a professor of pediatrics and chairman of infectious disease at the Medical College of Virginia Campus of Virginia Commonwealth University in Richmond.
His team published their findings in the Sept. 29 issue of the New England Journal of Medicine.
Cytomegalovirus is a very common infection that is usually harmless for adults and children, according to experts at the March of Dimes. About half of the U.S. population will have contracted CMV by the time they're 30.
But the virus can cause grave harm to newborns. About 1 percent of all babies born in the United States are born with congenital cytomegalovirus, an infection that varies in severity from causing no symptoms to causing severe neurological problems and even death.
There's currently no effective treatment for the infection, and if a mother is infected with the virus during pregnancy, there's about a 40 percent chance that she'll pass the infection on to her offspring.
Hyperimmune globulin is a type of immunotherapy designed to boost the maternal immune system. For the current study, CMV-specific hyperimmune globulin was used to ramp up the immune system against this particular threat.
Adler said the researchers suspected the CMV-specific hyperimmune globulin would work in humans because of prior research in human cell cultures and animals. The therapy is considered very safe, and no adverse effects have been noted.
Because the therapy is considered so safe for women and the consequences of an active CMV infection can be so severe for newborns, the study was not randomized and women were offered the option to receive treatment.
Pregnant women were recruited for the study from eight Italian cities. Women with active CMV infection were then separated into either a therapy group or a prevention group.
The therapy group included 45 women who had an active CMV infection, as did their babies. All babies were tested via amniocentesis. Thirty-one of these women elected to receive treatment with hyperimmune globulin, and 14 chose not to receive the therapy.
Only one woman (3 percent) in the therapy group gave birth to an infant with CMV disease, defined as a displaying symptoms of infection at birth and being in some way handicapped at 2 years or older.
In contrast, seven women (50 percent) of the women who weren't treated gave birth to babies with CMV disease.
The "prevention" group included 84 women with CMV infection who chose not to undergo amniocentesis, so the researchers didn't know whether or not these babies were infected. Thirty-seven of these women chose to receive hyperimmune globulin, compared to 47 women who declined.
Six out of the 37 women (16 percent) who received treatment delivered babies with congenital CMV vs. 19 out of 47 women (40 percent) who did not receive the treatment.
"This new therapy is very exciting because there has been no effective therapy for protecting babies from CMV," said Dr. Patrick Duff, from the University of Florida College of Medicine in Gainesville, and author of an accompanying editorial.
However, Duff added, "There's still room for caution here. This study didn't include a huge number of patients, and it wasn't randomized." He also noted that screening tests for CMV aren't 100 percent accurate and therapy with hyperimmune globulin is expensive. "There are still some loose ends," he said.
Both Adler and Duff said additional studies need to be done to confirm these findings.
In the meantime, Adler believes women who are pregnant or thinking of becoming pregnant should be screened for CMV -- especially if they are at high risk for infection. High-risk groups include women who spend a lot of time with young children, such as a teacher or day-care worker or a mother of a young child under the age of 2 or 3, he said.
Women who test seronegative -- meaning they've never had the disease -- need to take precautions to lessen the chance of getting infected with CMV while they are pregnant. This means frequent and thorough hand washing and avoiding intimate contact with youngsters -- no kissing on the lips or sharing eating utensils. Women who test seropositive -- meaning they've had the infection at some point in the past -- are at extremely low risk of passing any active infection onto their baby, however.
More information
The March of Dimes has advice on preventing CMV infections.
