Soon after Alabama emergency medical technician Kimberlie Durham discovered she was pregnant, she said her work situation felt untenable. Her duties required her to carry stretchers and other equipment but her doctor said she should not lift anything more than 50 pounds.

Durham’s employer, Rural/Metro Corp., an Arizona-based emergency services provider, said it could only offer unpaid leave for six months until she had her baby and refused to reassign her to a less strenuous job, according to a lawsuit she filed. Durham’s lawyers said the company’s decision clashed with federal laws that protect pregnant women in the workplace.