A third of the software engineers and developers out there are women. I am willing to bet though that the numbers in hot tech start-ups are significantly less than that.
And yet, what of the woman who says "I don't want to work this job while I raise my kid? I am going to become a freelance tech writer! (or developer, or whatever)" They don't count in these metrics. Which may also say something about the sexism latent in the metrics.....
BTW, two of the most talented programmers I have ever met in my life were women. One worked in academia, and the other, despite her important achievements, worked at a tech-centric coffee shop as a sysadmin, and later got a job as a developer for a relatively obscure yet stable company.