Re: Assumptions
Try getting hired in silicon valley with a grey beard,
I think ageism is the major cause of fewer women rather than outright sexism.
Increasingly you need a postgraduate degree to be considered at the hot big companies, so you start your career nearer to 25. If it's harder to get a job after 35 and any break means your experience of last years hot technology is obsolete - then it's a lot harder to take a couple of years out to have children than it would be in medicine or law.
The same thing happens in academia, it's often said that a PhD+postdoc costs you your first born child - but at least once you get a permanent job you don't have quite such a ticking clock.