Clearly, anyone born by caesarian delivery cannot be considered a "natural born citizen." However, there remains a great deal of uncertainty about some modern births. For example, if childbirth is assisted by an episiotomy, can the child still be viewed as a "natural born citizen" at birth? How about a ventouse delivery?
In 1738, Mary Donally, an Irish mid-wife, performed the first caesarian section in the British Isles. Just a few decades later and likely because of Donally's breakthrough, our Founders enshrined in our Constitution the requirement that our presidents be natural born citizens.
Most of our current uncertainty stems from the fact that there is no clear evidence that Donally was able to foresee the advent of episiotomies and ventouse deliveries. Thus, it will be necessary for us to guess whether Donally would have considered some of our modern procedures consistent with a natural birth.