The most important problem isn't that some women at the top struggle to have both an elite career and a fulfilling family life -- but rather that many women are scared to be ambitious

I don't think "scared" is the right word, to be honest. Upper middle class women that I know seem to proceed with public life until they reach a point where two things happen:

* They hit the negative consequences of their previous educational and career decisions

* They marry men of their own social class and usually greater income

These two things tend to hit right around the same time, and assisted by current ideology about upper-class childraising the net result is an inflection point where paid labor often comes to seem like more trouble than it's worth.

Of these two factors, I actually think the former is the more decisive. I've met an endless number of women who were humanities majors in college, and then took career paths which have petered out in unsatisfying ways. Let's be blunt: writing and soft skills are important, but in today's economy they are very often subordinate to hard technical skills. It must be exceptionally frustrating for intelligent women to get older and develop more leadership ability... only to learn that they lack power in their organizations AND ALWAYS WILL. Furthermore, there is often ferocious competition for soft-skills jobs as you climb the ladder -- often with other women. How sucky must it be to look around your company and realize there are 8 VPs of engineering but only 1 VP of marketing? I've noticed that the women I know who have strong hard skills -- like finance, science, technology, law, and medicine -- are also much more likely to stick with their careers even if they marry and have children.

The thing is, for any given individual this decision may in fact be perfectly rational. But for society at large, the outcome may be somewhat negative over time. Or maybe all those stay-at-home moms will eventually start a revolution that fundamentally changes the world for their daughters. Social change is often hard to predict, and the bigger the change the harder it is to see coming.