Does anyone know if aging affects the size and shape of a belly? For example if a woman at 50 would Carry differently than she did at 20.

As far as I recall, aging has little if any effect on how large a woman's belly would be and how it would be shaped; primary factors that affect the size and shape would be genetics, the amount of children a woman had before she got pregnant again, if the pregnancy is that of a multiple fare, her normal posture when standing up, her height, and if she's been eating well.

I guess I can think of possible effects of age on a preggo and that is skin elasticity and the amount of pregnancy spots that would appear on them: the former would definitely make a 50 year old preggo look a bit more haggard than a 20 year old preggo and the latter already on not just older pregnant women, but older people in general, although the latter I'd bet would be less frequent in appearance. And again, those can be influenced by genetic factors as well.

As far as I'm aware, age doesn't really have any factor in terms of the size of the belly. How women carry is purely down to the positioning of the womb/uterus. 

I would say the only real factor which may play a part in that would be down to how she has cared for her skin over the years - which would mean it may remain quite 'elastic' or not. It's only natural that this begins to deteriorate with age. It would be easier for a woman in her early 20's to 'recover' her figure more easily than a woman having a baby in her early-mid 40s for example.