Can I be demoted and have a paycut for being pregnant?

I've had a complicated 1st trimester of pregnancy and have had some absences. My employer knows my absences have been pregnancy related. I have been given the go-ahead by my doctor to work but only the AM shift, full-time. I've been told by my employer that there's a possiblity I will be demoted due to business needs and take a paycut since they have to think about he business first. Can they do that?