I think that it is perhaps not an automatic career choice for females, either because it is seen as a 'male' career, or because there aren't many female-pilot role models who young girls can relate to.
That may seem like a rational reason but, I do believe, on the face of it, most women are just not interested in flying. Simple as. Nothing to do with role models and gender stereotyping (and women themselves can be just as guilty of this as men). After all, Pilot-Chick and Daria-Ox, did you you need a role model to arrive at your career choice? I'm guessing not!
The "issue" of pregnancy and children is something that affects many employment sectors, not just aviation. For example, a veterinary student and employer will invest a lot of time and money into training and qualification; however, veterinary practices don't use "potential pregnancy" as an excuse not to employ women (aside from it being illegal to use it as a reason!) as there is an equal mix of male and female vets. Plus there are also paternity leave rights now!!!
And Daria? Not all women want or can have children!!
Cheers
Whirls