Different companies have different policies. See if you'll be receiving full or partial salary, if any. Companies aren't required by law to offer any sort of paid maternity leave, so even if you work for a large company, you may not be entitled to paid leave. While the FMLA guarantees leave time, it doesn't guarantee that you'll be paid.
It's important to know your rights before the big day arrives. Talk to someone at human resources and to other women in your office who have taken maternity leave to see if they have any tips.