Decrease in seroprevalence for herpesviruses among pregnant women in Finland: cross-sectional study of three time points 1992, 2002 and 2012.

Maternal herpesvirus infections during pregnancy may cause fetal and neonatal infections. We investigated the seroprevalence of five herpesviruses: cytomegalovirus (CMV), herpes simplex virus (HSV) 1 and 2, varicella zoster virus (VZV) and Epstein-Barr virus (EBV) in randomly selected samples from pregnant Finnish women from the years 1992, 2002 and 2012. Over 20 years, the seroprevalences decreased significantly for CMV from 84.5% to 71.5% (p = 0.007) and HSV-1 from 69.5% to 45% (p < 0.001). The decrease in seroprevalence for HSV-2 (from 17.5% to 11%) was not statistically significant. The seroprevalence remained unchanged for VZV and EBV. The proportion of mothers with no antibodies to either HSV-1 or HSV-2 increased from 25.5% to 48% (p < 0.001). The seroprevalences for HSV-1 and HSV-2 increased in relation to age, which shows that women of childbearing age do contract primary HSV infections. Our findings indicate that a considerable proportion of women (48%) are at risk for primary HSV infection during pregnancy.