A vaccine is offered to healthcare workers (doctors, nurses, etc) who have not previously had chickenpox.

http://www.patient.co.uk/health/planning-to-become-pregnant

A vaccine is offered to healthcare workers (doctors, nurses, etc) who have not previously had chickenpox and so are not immune and may catch chickenpox. (About 1 adult in 10 has not had chickenpox as a child.) Therefore, non-immune healthcare workers should consider having this vaccination before getting pregnant.