Hi,
I work shifts too, 8-8, mostly 2 days and a night with three or four off. In the ambulance service, but they give you the option to go on light duties at any time. I'm in an office at the moment and there is no way I could do shifts and be pregnant, totally shattered, nausea etc I would be throwing up in the back of the ambulance all over the patient, not what you really wanna do!!!
All employers are meant to evaluate you job and give you the option of something else more suitable and if they can't find you anything (which is bound to be very rare) they pay you normal salary and you stay at home. Ask for their policies and procedured regarding pregnancy.
Good luck.
Bev x x