Parents: did you worry about the possibility of your future children having a disability?

I don't have any children but my husband and I might have children one day. I currently teach full time in a special education class in a school and part time for an early intervention program. Since I have been in this field, I have seen a little bit of everything in terms of disabilities and developmental delays. Is it normal to worry about having a child that might have possible delays?? I worry about autism as I see so many people with spectrum disorders and the diagnoses are increasing at an alarming rate. I also worry about other conditions like muscular dystrophy, cerebral palsy, mental retardation, etc. Is this normal? Do all parents and parents to be think of these things before children? Or maybe because I'm overexposed to it and see it daily it becomes more real?