Yes. The Ionising Radiation Regulations 1999 place additional duties on your employer while you are pregnant or breastfeeding. Provided you tell your employer in writing that you are pregnant, your employer must make sure that you are not exposed to more than 1 mSv for the rest of your pregnancy. This is roughly equivalent to the radiation your baby will receive through natural sources of radiation outside work.
Your employer should carry out a risk assessment, and if you work in areas where exposure is likely to exceed 1 mSv, your employer must change your working conditions. For example, if you are a nurse on a radiotherapy ward, this might mean using bed shields, spending less time with patients, not working with certain patients, and not cleaning up radioactive spills.
The Health and Safety Executive (HSE) has produced a booklet: Working safely with ionising radiation: guidelines for expectant or breastfeeding mothers.