How does a baby get herpes? Is it a serious problem?

In most cases, transmission of HSV to the neonate occurs by delivery through an infected birth canal. Postpartum acquisition occurs less commonly. Development of primary or initial non-primary genital herpes by the mother at or near the time of delivery poses a significant risk for the infant. However, most cases of neonatal herpes are the result of asymptomatic shedding in women with no known history of genital herpes. The usual onset of neonatal herpes is 5 to 21 days following exposure. Approximately 80% of infected neonates have at least some characteristic skin lesions. Herpes infection in the neonatal period can be devastating because of the inadequate immune response seen in neonates.

Corey L, Wald A: Maternal and neonatal herpes simplex virus infections, N Engl J Med 361:1376–1385, 2009.