When is the highest risk period for parvovirus infection during pregnancy?

The highest risk period for parvovirus infection during pregnancy occurs during weeks 13 to 16. In this timeframe, the fetus is particularly vulnerable to the effects of the virus, which can lead to severe complications including fetal anemia, hydrops fetalis, and even fetal demise, due to the greater likelihood of fetal infection and the developing fetal circulation.

During the first trimester, while the implications of parvovirus infection can still be significant, the risk of serious fetal outcomes is more pronounced once the fetal organ systems are more developed, which corresponds to the 13 to 16 week period. Additionally, infection in the second trimester, particularly weeks 13 to 16, aligns with increased incidence of fetal anemia as the baby begins to produce its own red blood cells. In the third trimester, although parvovirus can still pose risks, the likelihood of severe congenital complications tends to decrease compared to earlier gestational ages when the fetal systems are still maturing.

Thus, the timing at which fetal exposure to parvovirus poses a higher risk for adverse outcomes is notably centered around the second trimester, specifically weeks 13 to 16, making this the most critical window.