But under the Pregnancy Discrimination Act, an employee who is pregnant has to be treated the same way as an employee who is not. So it is relevant whether a similarly situated employee who had emergency surgery to remove an appendix would have been treated the same, even if there is no disability as defined by the ADA.
Two things I am tired of typing: 1.) A wrongful termination does not mean that you were fired for something you didn't do; it means that you were fired for a reason prohibited by law. 2.) The above answer, whatever it is, assumes that no legally binding contract or CBA expressly says otherwise. If it does, the terms of the contract apply.