Marissa Mayer, one of the top executives at Google, will be the next CEO of Yahoo, making her one of the most prominent women in Silicon Valley and corporate America.Ms Mayer has blazed several trails in the tech industry. As employee number 20 at Google, she was the company’s first woman engineer and ended up being one of its most high-profile executives when she oversaw its search business.Now she’s blazing many more new trails. Female CEOs at tech companies are incredibly rare and for them to 30-something is even more rare. Now, Ms Mayer has announced she is due to give birth to a baby boy in October — making her quite possibly the first pregnant CEO of a publicly traded Fortune 500.The 37 year old whose first job at Google was computer programming, was later put in charge of the company’s location and local services, including Google Maps — overseeing more than 1,000 project managers. She has, for years, been responsible for the look and feel of Google’s most popular products: the famously unadorned white search home page, Gmail, Google News and Google Images.Ms Mayer has sat on Google’s operating committee — part of a small circle of senior executives who had the ear of Google co-founders, Larry Page and Sergey Brin. She has been one of the search giant’s most visible and powerful executives, often tapped for keynotes at technology conferences and glamorous magazine spreads.The appointment of Ms Mayer is a surprising coup for Yahoo, which has struggled in recent years to attract top talent in its battle with competitors like Google, Microsoft and Facebook. She’s the fifth CEO in five years as the company tries to rebound from financial malaise and internal turmoil. Fred Amoroso, Yahoo's chairman, says the board was drawn to Mayer's "unparalleled track record in technology, design, and product execution."As President and chief executive, Ms Mayer joins a shortlist of women in Silicon Valley who hole the top spot — an elite club that includes Meg Whitman, CEO of Hewlett-Packard, and Virginia Rometty, the head of IBM. Another senior woman in Silicon Valley, Sheryl Sandberg is Facebook’s chief operating officer.In recent months, Ms Mayer has started to find success outside of Google. In April, Wal-Mart, the world’s largest retailer tapped Ms. Mayer to join its board, her first seat at a public company. She is one of four women on Wal-Mart’s 16-person board.