It's not an issue for all babies - if their mother has been infected with herpes virus pre-pregnancy, they pass on some immunity to the child. That's why it's not an issue for most babies.

However.

If the mother has never had herpes or the baby has immune issues or is premature, the baby is vulnerable (and that's what could be the case here). If the mother acquires herpes in the third trimester, the baby may be born with it. If the mother has an active genital herpes outbreak at the time of birth, the baby may be born with it. This happens to about 1 in 3000 babies and it can kill.