Your employer does not owe you any notice or warning of moves: your employer is free to move its operations at will for its own benefit without any regard for the impact on employees. (This is one of several consequences of "employment at will": the legal doctrine that employees do not have any right to their jobs, but work rather "at the will" of the employer.) Your employer only needs to give you the opportunity to work at home IF doing so is reasonable for it given the nature of your job, how you work with other persons in the company or with clients/customers, tools or equipment or resources you need, etc. If it would be disruptive to them, reduce productivity or increase costs by more than a nomimal amount, or be impractical, they do not have to let you work at home: an employer's obligation  is simply to make "reasonable accommodations" to your pregnancy, which means changes that are not too disruptive or expensive. If working at home is not something that can really be done for your position and how this company works, they do not  need to let you do this.