The FMLA as far as I know allows for 12 weeks in one ear unpaid leave.. I went through human resources with my first little one. Because there is a form you have to fill out and have your doctorr sign but you can make the family leave act retro-active for example if you go into labor on a teusday and fill the paper work out on a friday..that is fine. Also if you have short term disability that should cover maternity leave too.
I told my bosses the day I found out (I was bursting with excitement, so they kind of knew something was up) I went and talked to my HR rep and she helped with everything. I work for NY state and they have quite a few angles on how to get the ins and outs of requesting time off. They should be able to help you.
the act is called the FMLA leave, it is a leave that grants 8 weeks unpaid leave to anyone who has a life changing event, like a baby. You have to be there for a year a qualify. Your position has to be available when you go back (if it is in the 8 week period and you have a position that isn't higher up like a manager) and your pay cannot be cut. There is a document you print out and fill out that your HR can get for you.
My work knows I'm pregnant and knows when i plan on taking my leave. Which I am going to try and work until labor. We haven't sent for how long, but i'll probably go in for a few hours here and there. I just straight out told my boss, however I havent worked there for a year once the baby comes but I think they will keep my position.
I would just write a letter stating your pregnancy and when you would like to take your FMLA leave, with FMLA leave you really just have to give as much notice if a family member grew ill there obviously wouldn't be much time for notice so I do not believe there is a deadline. And if you work until labor you really can't give a notice since you do not know when labor will arrive.
I work in the office so i've handled this for others. Let me know if you have any other questions.