While there are a wide range of articles about the benefits of vaginal birth, which appear to include better expulsion of fluid from the lungs, better immune response in childhood and so on, there doesn't seem to be any definite medical proof. Have a look at this unresolved [question over on Skeptics][1].

There doesn't appear to be any indication that children born through vaginal childbirth are any smarter, either. After the initial childhood stages it doesn't appear to be possible to identify which individuals were Caesarian or natural.

Caesarian sections do have a major effect **on the mother**, however - major abdominal surgery means the mother can't lift things, drive, or even move easily for many weeks.


  [1]: https://skeptics.stackexchange.com/q/9994/619