Birth defects from mom's West Nile infection rare

By Will Boggs, MD

NEW YORK (Reuters Health) - Birth defects appear to be uncommon in infants born to women infected with West Nile virus (WNV) during pregnancy, according to a new report.

"The current study's findings are overall reassuring in that the majority of the women for whom there was information delivered apparently healthy infants with normal growth and development," Dr. Daniel R. O'Leary from Centers for Disease Control and Prevention, Fort Collins, Colorado told Reuters Health.

O'Leary and colleagues studied 77 pregnant women with WNV illness. Twenty-five women were believed to have been infected during the first trimester, 27 in the second trimester, and 24 in the third trimester. Time of infection was unknown for 1 woman.

Four women had spontaneous abortions, two had elective abortions, and the other 71 women delivered 72 live infants, including one set of twins.

The frequency of spontaneous abortion, preterm delivery, and delivery of low birthweight infants was no higher in this group than expected in the general population, the authors report.

Seven infants had major birth defects, the results indicate, but only three of these defects could have been caused by maternal WNV infection, based on the timing of the infections and the sensitive developmental period for the specific malformations.

In none of the infants with major malformations could researchers find any conclusive evidence that West Nile virus played a role.

"The current study was conducted in follow-up to the first documented case in 2002 of human congenital WNV infection in an infant with severe neurologic birth defects," O'Leary explained. Because no new cases of congenital WNV infection were confirmed, "the 2002 report is still the only documented congenitally acquired WNV case to date."

SOURCE: Pediatrics March 2006.