Since she was 18 at the time, Obama's mother could not possibly have met the requirement to be resident in the US for five years after the age of 14.
By that logic, any woman giving birth before the age of 19 could not meet the requirements, even if they'd never left the country. There would have to be more to it than that.
"A casual stroll through the lunatic asylum shows that faith does not prove anything." - Friedrich Nietzsche