Giving notice at work--What can my employer do once this happens?

I live in IL and, due to poor working conditions as well as my pregnancy, I've decided that I no longer want to work at my place of employment. I have not told them I'm pregnant yet (I'm 4 months). I was thinking of giving a 2 months' notice on my resignation. Once I do this, can they let me go before my resignation date? If they do, are they still obligated to pay me up to the proposed date of my resignation? It's an organization with under 50 employees.