This is the second time that the 40-year-old Mayer has given birth since Yahoo hired her as CEO in July 2012.

She and her husband have a 3-year-old son, Macallister. A Yahoo spokeswoman declined to reveal the twin' names or weights.

Mayer yesterday announced that Yahoo will spin off its Internet operations into a separate company.

As she did with her son, Mayer plans to only take a 'limited' time away from her job. She has been working on a cost-cutting overhaul of Yahoo that she plans to discuss next month.