We cannot get enough women into tech fields, the pipeline is far from full. A further problem is that once women do get into tech jobs, they often leave in mid-career.
Women Technologists Count, a report from the Anita Borg Institute, takes a look at the reasons why women in mid-level jobs tend to leave technical career paths to become managers and/or leave the industry entirely.
An article at Fast Company, Why Women Leave Tech Companies, And What To Do About It, details more about the study and its findings. The article includes an infographic which summarizes the findings. I suggest you read the full article in addition to taking a look at the infographic.