Mummy's with babies and dogs?

We have a huge dog, who was mistreated also. We were not sure how she acts around kids, but from kids that have been here she has been fine. But, they have always left. Now that baby is here permanently we have put some stair gates up in the door ways so she can see in and see that bubs is still here and bubs is protected from her. You can never tell with dogs, especially rescue ones. Its unfortunate but I don't want to take the risk.