When taking FMLA for pregnancy what paperwork do you need to fill out for medical certification?

I am planning on taking 6 weeks short term disability through my work for my pregnancy and I want to take the last six weeks on FMLA leave. What is the process for taking FMLA leave? Do I need to fill out some sort of application for that or what?? And do I have to have medical certification for pregnancy on FMLA leave?