Maternity leave question.

So I recently found out that it's state law that I get 12 weeks off for maternity leave from work. I called my dr office today and spoke w the insuarance lady and she told me they won't write me off for 12 weeks they will only write me off for 8 weeks at most. So my question is how in the world do I go about getting 12 weeks off!? Oh and I live in Ohio if that makes any diff.