The rules on this apply equally to full and part-timers, and vary between Colleges. European legislation allows exemption from on-call if breast-feeding, and you should be able to obtain exemption, or other modification of working hours, if you are pregnant. If there are good reasons for not doing on-call, it may be possible to obtain educational approval for emergency work that is done within the working hours of 8.00 a.m. to 7.00 p.m. Most Colleges will treat applications for exemption on an individual basis, and you should contact them directly.