Yahoo CEO Marissa Mayer expecting twin girls

One of the most powerful women in the technology sector is expecting identical twin girls.

Yahoo Inc. chief executive Marissa Mayer announced in a Tumblr post Monday that she is pregnant with twins due in December. She described the news she was having twins as "quite a surprise."

Mayer's pregnancy is bound to play into the debate in Silicon Valley over how parents working in technology can manage a young family.

In her post, she indicates she may return to work very soon after giving birth.

"Since my pregnancy has been healthy and uncomplicated, and 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," she wrote.

Mayer took just 2 weeks leave

With her son, born in September 2012, Mayer returned to work just two weeks after giving birth. She had been hired as Yahoo CEO while pregnant.

She used her own money to build a nursery next to her office.

Mayer received criticism from other women working in technology for taking so little time off. The sector is notorious for its long hours and high expectations, which can discourage young parents.

In April 2013, Mayer doubled the amount of time women at Yahoo could take as paid maternity leave to 16 weeks. Fathers are eligible for up to eight weeks.

Then she received flak for stipulating that employees couldn't work from home, eliminating an option for parents of young children. Mayer said she believed the company benefited from ideas-sharing when everyone is in the same place.

The U.S. has no labour laws mandating paid maternity leave, though mothers are entitled to 12 weeks off.

Still, some companies are moving to retain more women by offering more paid leave. Netflix increased maternity leave to a year, and Microsoft, Adobe and Apple have all increased the amount of time mothers can have off with pay.