Yahoo CEO Marissa Mayer is pregnant! The 40-year-old took to her personal blog to announce the exciting news with a post titled "Happy Personal News." "With great happiness, Zack and I have some exciting news to share — I'm pregnant!" she wrote. "In fact, I'm expecting identical twin girls, likely arriving in December."

Mayer and her husband Zack Bogue already have one son, who was born in 2012, just three months after she assumed the top spot at Yahoo, according to Yahoo News. They're excited to be having twins, even though it came as "quite a surprise."

"I have no family history of twins or any other predisposing factors," she continued in her blog post. "However, as I've now learned, identical twins occur by random choice in roughly 1 out of approximately every 300 pregnancies. Zack and I have embraced the surprise and are very excited about these new additions to our family."

When her son was born, Mayer took it upon herself to extend the company's parental leave policy to 16 weeks of paid leave for mothers and eight weeks for fathers, according to the Wall Street Journal. Yahoo also gives new parents a $500 bonus to spend on certain expenses to care for their child and help their family.

Mayer has been chief executive for three years now and is looking for ways to bring new direction to the company. As for her intense role at the corporation, she will only be taking "limited time away" from work during her pregnancy, and she's lucky and happy that Yahoo's board of directors have been "incredibly supportive."

"Moving forward, there will be a lot to do for both my family and for Yahoo," she continued. "Both will require hard work and thoughtful prioritization. However, I'm extremely energized by and dedicated to both my family and Yahoo, and will do all that is necessary and more to help both thrive. The future looks extremely bright on both fronts."