Yahoo CEO Marissa Mayer expecting twin girls in December

Marissa Ann Mayer, president and CEO of Yahoo!, arrives for the Metropolitan Museum of Art Costume Institute Gala 2015 celebrating the opening of "China: Through the Looking Glass," in Manhattan, New York May 4, 2015. REUTERS/Andrew Kelly

(Reuters) - Yahoo Inc Chief Executive Marissa Mayer said she was pregnant with identical twin girls, likely due in December, but promised she would take limited time away as she works toward turning around the company's struggling online ad business. Yahoo is also preparing to spin off its stake in Chinese e-commerce giant Alibaba Group Holding Ltd and is considering the future of its holding in Yahoo Japan Corp <4689.T>. Yahoo shares fell 1.5 percent at $31.77 in morning trading amid a selloff in the broader market. "Since this is a unique time in Yahoo's transformation, I plan to approach the pregnancy and delivery as I did with my son three years ago, taking limited time away and working throughout," Mayer wrote in a blog post on Tuesday. Mayer, 40, was pregnant when she joined Yahoo as CEO in July 2012 and gave birth to a baby boy in September that year. Mayer worked from home after the birth and came back to the office just two weeks later, stoking a debate about whether her example would help or hurt the cause of women in the workplace. ( Media reports that Mayer paid to have a nursery built next to her office further fanned the controversy. The company also sparked nationwide outrage in early 2013 when it banned working from home, a policy critics said would make life difficult for working parents. Later that year, Yahoo increased the amount of paid leave new mothers can take to up to 16 weeks and introduced eight weeks of paid leave for fathers. Previously, mothers could take eight weeks, while no paid leave was offered to fathers. U.S. technology companies including Netflix Inc and Microsoft Corp have recently increased maternity leave as a way to keep and attract staff. Yahoo said in its corporate blog on Tuesday that it was "extremely happy" for Mayer and supported her plans and approach. ( Mayer, who has been married to start-up investor Zachary Bogue since 2009, was an executive at Google Inc before taking the helm at Yahoo in 2012. Mayer has a net worth of about $380 million, according to Forbes. Her pay package jumped 69 percent to $42 million in 2014, mostly due to gains in Yahoo's stock price despite concerns about the health of its business. (Reporting by Supriya Kurane and Devika Krishna Kumar in Bengaluru; Editing by Ted Kerr and Sayantani Ghosh)