No, I am pretty sure you still use the STD..at least in talking to my benefits counselor ..and use your leave when it runs out. ie I have enough leave to extend my 6 weeks by a few weeks, I will take the 80% paycheck for 6 weeks, then use my leave to get a normal paycheck for the next couple weeks.
Also, most STD's have a waiting period to kick in if you are not hospitalized right away..meaning if you are on bedrest for say, 2 weeks before you give birth, and your waiting period is 7 days (mine is, as an example) then you would have to use your own leave for a week to get paid before the std kicks in. If you work one day and have the baby the next, it starts automatically..
kinda confusing..I had a long talk with my benefits person..because it isn't something I have ever done before..I would suggest that to anyone looking on this thread..they get these questions all the time..though I think most work in the same way.