Just that really.
I think about how lucky I was to never have any morning sickness or back pain or swollen ankles. I was overweight at the time of getting pregnant the second time and had only had my first twelve months before. Even running about with a toddler felt relatively easy and photos of the time show me looking happy and relaxed (sort of.) This isn't a brag honest!
My friend is already having frequent days off with sickness when she is younger and healthier than I was when I conceived my first. My other friend had morning sickness so bad she seriously considered whether she could continue the pregnancy. Do medics understand what makes some people breeze through pregnancy and not others?
With mine I found out late both times (eight weeks with number 1 and six weeks with number 2) so I can't have had much in terms of physical symptoms.
Just from anecdotal evidence, I feel there is no correlation between the lifestyle of the mother and how difficult a pregnancy you will have.