Beware of plastics in clothings and use organic clothings. use no pans with weird layers inside of them to prevent getting those in you.
Discussion
Train the immune system of your child. and another tip: maybe make sure that the cellular tissue is strong and endurable so in case of potential cancer, that the cells wont break and come in the bloodstream easily.
Also, keep in mind that the first line of defense in any attack is the person itself. Make sure your child knows how to run, knows her / his potential, so that when it is needed, the child knows how to escape or buy precious time. You got a whole childhood to face: success!
(sorry if it seems like I wanna dictate the raising of your child: this is not the case. I just want your child to be as healthy as possible!)