The gel is usually used to get you to about 3cm before they break your waters i think. From memory you have to be dialted a certain amount to break your water. I would think breaking your water should bring on labour by itself as you have already started dialating so your body must be ready for bub to come out IYKWIM. I dont think it would be safe to break your waters and then use the gel... I dont think they would do that.