Polyhydramnios

I am pregnant with my 3rd child and have Polyhydramnios. A diabetes test come back clear and in a couple of weeks I have my 28 week scan looking into it under the fetal medicine department, I am not to sure what a scan under this department means and also what else it means to have this fluid when diabetes is clear. Has anyone else been through something similar and can offer some insight? (And re assurance) thanks