With genital herpes, how can a man give his wife a baby without giving her herpes?

Take antiviral meds. A fetus (unborn baby) can catch herpes from the mother before labor and delivery. Such transmission of the herpes virus is uncommon but does occur sometimes. It happens more often if the mom catches herpes for the first time while she is pregnant. Most of the newborns with herpes caught it during or soon after the birth process. The mother can take antivirals from late pregnancy through delivery.
Yes. The transmission of herpes is not 100% with contact but increases with any breaks in skin or contact with mucosal membranes.