That's because, during these times, your body's immune system may be less able to suppress the virus and keep it from becoming active.
Once the virus enters through the skin, it travels along nerve paths.
It may become dormant (inactive) in the nerves and remain there indefinitely. When that happens, the virus travels back along the nerve path to the surface of the skin, where additional virus is shed.
That's why taking steps to prevent an outbreak at time of delivery is recommended starting at 34 weeks into the pregnancy.
If you have signs of an active viral infection when it's time to deliver, your doctor will likely recommend a cesarean section for delivery.
People with genital herpes have a higher risk of an HIV infection.