West Nile Virus and Pregnancy
Some expectant parents have concerns about West Nile virus and pregnancy. Based on the limited number of cases studied so far, it is not yet possible to determine what percentage of West Nile virus infections during pregnancy result in infection of the fetus. Pregnant women who think they may have become infected with West Nile virus should contact their healthcare provider.
Women who are pregnant should be aware of West Nile virus symptoms and prevention strategies. This is because it is possible (although unlikely) for a pregnant woman infected with the West Nile virus to pass the infection on to her unborn child.
Based on the limited number of cases studied so far, it is not yet possible to determine what percentage of West Nile virus infections during pregnancy result in infection of the fetus, or medical problems in newborns.
In 2002, one case of transplacental (mother-to-fetus) transmission of WNV was reported to the CDC (Centers for Disease Control). In this case, the infant was born with WNV infection and severe medical problems. It is unclear, however, whether WNV infection caused these problems or whether they were due to other causes.
After the report of this case, the CDC and state and local health departments formed a registry to follow birth outcomes among women with WNV illness during pregnancy. Three additional pregnancies in which the expectant mother became infected with WNV were detected and evaluated in 2002; none of these three resulted in fetal infection. In one additional case it remains unclear whether the fetus was infected, because appropriate testing was not done.
In 2003, the registry identified 74 women who acquired West Nile virus illness while pregnant. As of May 10, 2004, 62 of these women had delivered live infants, 2 had had voluntary abortions, 5 miscarried in the first trimester, and 5 had not yet delivered.