If you have had chickenpox in the past, it shouldn't be a problem now. If you haven't had chickenpox, exposure during the first trimester can result in birth defects, including heart problems. Exposure close to delivery (within 1 week) can result in chickenpox in the baby.
Adults don't tolerate chickenpox as well as children. They may have serious symptoms, including painful lesions, high fever and severe flulike symptoms.
If you are not sure if you have been exposed to chickenpox in the past, avoid exposure to the disease if you can.