I came across this article from a few weeks ago: Women of Mad Science, posted by Mad Scientist Journal. The question they pose is, "Why Aren't There More Woman Sci-Fi Writers? Not a new question, but an interesting one. There are some good points--and I added my two cents to the comments.
If the topic interests you, I'll leave you to give the article a read (and add to the discussion of you wish) rather than reproduce it here. I'll be interested to see any new comments that come up.