I got sick the day I took DD home from the hospital and it lasted 6w. There is nothing you can do. Wash your hands often, don't touch your face and don't cough/sneeze in their face.
We're a pass around family; everyone gets every cold, usually in the order DS1 -> DS2 -> Me -> DH, but sometimes I get it from DS1 first. I just do all the usual don't get everyone sick things, like coughing into my sleeve, using tissues and hand sanitizer, washing hands often. Even if I'm sick as a dog, I'm at least going to be nursing, so there's not much no-contact that I can do.
Re: What if momma gets sick?