What is the risk of herpes simplex virus (HSV) transmission from a mother to her infant?

Updated: Feb 27, 2019
  • Author: J Michael Klatte, MD; Chief Editor: Russell W Steele, MD  more...
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At the time of vaginal delivery, the risk of herpes simplex virus transmission from a mother with true primary herpes simplex virus infection to her infant is approximately 50%. Women with primary infections at delivery are 10-30 times more likely than women with a recurrent infection to transmit the virus to their babies. [19] Infants born to mothers with newly acquired infections who do not have primary infections in the presence of preexisting immunity caused by another viral infection (ie, first-episode nonprimary) have a transmission risk of 25-30%. [39]

The neonatal herpes simplex virus infection rate is considered to be less than 2% when the mother has active infection caused by the shedding of herpes simplex virus acquired before pregnancy or during the first half of pregnancy (recurrent infection). Approximately two thirds of women who acquire genital herpes during pregnancy have no symptoms. [31, 40] Of mothers who deliver an infant with herpes simplex virus infection, 60-80% have no evidence of genital herpes simplex virus infection at the time of delivery, have no history of previous genital herpes infection, and have sexual partners without a reported  history of genital HSV infection [41] . Of babies born to mothers with a primary infection near the time of delivery, 30-50% acquire the infection.

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