Also, personally, I think that nothing could be more counterproductive than a lawsuit. They are negative and drag on for years. You should be enjoying your baby, instead. Also, suing an employer often makes it very difficult to get another job in the area. Although this is a surprise, it is not the end of the world.
I have to agree with you on the "not being the end of the world" comment. My wife lost her job 2 years ago, took another job that was totally misrepresented to her (instead of a 40 minute drive, they were sending her 2 hours away each day); she quit because of this, and thus lost her unemployment. However, she has been able to get temporary work since then, in hopes that she'll land a more permanent job as a teacher (teaching jobs are next to impossible to get in our area).