Although three-quarters of health care workers are female, women are under-represented at the top of health care organizations, with women comprising only 12 to 18 percent of hospital CEOs, according to a new study examining gender disparities in health care employment.

If these numbers hold up, they suggest women face more obstacles to reach the top spot in health care than in other industries. The Bureau of Labor Statistics says women make up about 25.5 percent of CEOs nationwide, according to the article.

The study, published last month in the Journal of Health Care Leadership, argues that women have a tough time breaking into hospital leadership positions.

Women make up about 76.5 percent of hospital workers, according to 2010 BLS figures cited by the study. The BLS doesn't provide gender breakdowns on hospital CEOs, so the authors of the study, led by Mary Ann Keogh Hoss, with Eastern Washington University in Spokane, Wash., had to make some extrapolations to find out the gender ratio of hospital chiefs. Primarily, the researchers used two recent surveys, the Thomson Reuters Top 100 Hospitals and a report on Washington state hospitals.

The survey of Washington hospitals found about 18 percent of hospital CEOs in that state were female, while 12 percent of the chiefs of the hospitals that made Thomson Reuters' list were women.

"Simply put, the status of women rising in the ranks in health care leadership in CEO positions has not changed in the past three decades," write the authors. "For the numbers of women working in the health care workforce, their numbers are not represented adequately at the CEO level."

Why are women underrepresented? No one knows for sure, of course, but the authors throw out a few suggestions, such as management favoring "masculine," competitive leadership styles, or the lack of initiatives to recruit more women for the C-suite.