The difficulty in getting more young women into science and high-tech fields has received a lot of attention recently, including from a new national mentorship program for budding female scientists as well as Super Bowl ads for engineering toys designed for girls.

But keeping women in those fields — and helping them reach the top — may be an even bigger challenge. A report released Wednesday by the Center for Talent Innovation (CTI), a research think tank founded by economist Sylvia Ann Hewlett, finds that U.S. women working in these fields are 45 percent more likely than their male peers to leave the industry within a year.

In addition, the study also found that nearly one-third of senior leaders — both men and women — who work in science, engineering and technology fields reported that a woman would never reach the top position in their companies. “Even the senior guys who are in a position to make change for the women in their company don’t feel like they can do it,” said Laura Sherbin, the director of research for CTI. When that’s the case, she asks, “what’s left?”

The report is an update of CTI’s 2008 report on women in high-tech jobs. It also found an exodus of women from these fields. The most recent survey sampled 5,685 college-educated adults with experience in a private-sector science, engineering or technology company; 2,349 of the respondents were women.

One key difference between the two reports is that this year’s study also looked at the experiences of women who work for science and tech companies in emerging markets. The results in these countries were similarly unsettling. More than a quarter of U.S. women in these industries say they feel stalled in their careers, while in India the rate is 45 percent. Thirty-two percent of U.S. women in such companies say they are likely to quit within the year, and the rate is nearly the same in China.

The study finds that gender bias underpins why these women either don’t think they can get ahead or are choosing to leave their organizations. One-third of U.S. women in what the report calls “lab-coat, hard-hat and geek workplace cultures” feel excluded from social networks at their jobs (that number is 53 percent in India). Meanwhile, 72 percent of women in the United States and 78 percent of women in Brazil perceive bias in their performance evaluations.

Finally, 44 percent of U.S. women reported feeling as though they were being judged against male leadership standards, asked to walk the famously tricky line between aggressiveness and assertiveness that can often derail women’s careers. Although that happens in most workplaces, Sherbin said, “it’s very extreme in these cultures. When the prevailing leaders are all men, it’s very difficult for women to look, act and sound like the leaders they succeed.”

For all that discouraging news, there were some bright spots. Fewer women in this year’s study said they were the lone woman on their teams. Eighty percent or more of women in each country said they loved their work. And more than half of U.S. women, as well as even greater majorities in emerging markets, reported having ambitions to reach the top. Their intent to leave these companies, Sherbin said, “clearly isn’t because they’re afraid of hard work. They feel stalled in their careers, and this feeling of being stalled turns into a massive lack of hope.”