Marissa Mayer is a trailblazer. A game changer. An elite engineer. A specialist in artificial intelligence. A cupcake enthusiast. A rare female executive in Silicon Valley. She’s Yahoo’s new CEO and she’s seven months pregnant.

Mayer has been defying expectation for years: she was Google’s first female engineer, their 20th employee, and worked on some of their flagship products, including Google maps and Google’s homepage. She’s also nearly 20 years younger than any other CEO (the average age for CEO’s in Standard & Poors’ 500 is 56.5). When Mayer stepped into the role yesterday, she became the 20th woman to be running a Fortune 500 company in America.

Yahoo! inc. have not had much luck with CEOs in the past year. You’ll probably remember the most recent - Scott Thompson, who didn’t let the truth get in the way of a good CV. His predecessor, Carol Bartz, famously announced to her team she had been fired over the phone in September 2011. Mayer was chosen over Ross Levinsohn, who has been interim CEO since Thompson sheepishly exited the role two months ago and broadly expected to stay in the role.

The fact that Mayer was a 37-year-old pregnant woman working at a rival technology company did not make her the obvious choice. Yet, here she is - flushed with the challenge of reviving one of America’s original tech giants. This is spectacular news.

It will be fascinating to see how Mayer takes on The Big Four of the internet scene: Google, Apple, Facebook and Amazon. After 13 years at Google, her intimate knowledge of their company will surely help. For some time now, Yahoo’s brand has been much stronger than its finances. To give you a quick idea of the disparity in share price between the companies - Google (GOOG) is trading at $576.73 USD this morning, and Yahoo (YHOO) sits at $15.6 USD.

Yahoo’s sales dropped 21 per cent to US$4.95 billion last year.

Mayer is Yahoo’s best bet to stem this downward spiral and lift the company’s profit margin. She is yet to reveal her vision for the company (understandable, she’s barely had time to choose a screensaver at her desk), but we wait with grand expectations. Judging by her track record with product innovation, I’d say she’ll start by bringing Yahoo’s mobile capabilities up to speed with its competitors. From there, who knows! It’s exciting.

Mayer has a bachelor’s degree in symbolic systems and a masters degree in computer science specializing in artificial intelligence from Stanford University. Her meticulous training in computer science gives her an enormous advantage as CEO, because she understands the minutiae of every code and product. She speaks fluent Engineer, and the product developers and programmers will love her for it.

Mayer’s fondness for cupcakes is also well documented, potentially of course because cupcakes are the culinary emblem of femininity. The implication, I suppose, is that she can declare a love of diminutive, girly baked goods and retain professional dignity in a man’s world. I’m not sure exactly why ‘Marissa’s favourite snack’ is important news, but cupcakes are delicious so I’ll let it slide.

People worldwide are chatting about Mayer’s maternity plans. She says she'll only be taking a few weeks leave to have her baby in October, and will be working while she's gone. I can't decide whether to shudder or smile, imagining Mayer with baby in one arm, phone in the other, balancing a laptop on the bed. I admire her immensely, and respect her decision. She’s just proven that the possibility of reproduction should not be a deterrent to recruiters or company boards, but at the same time she’s undermined the need for fair, extended maternity leave. It’s so complicated, for a woman in power.

I have so many questions for Marissa: What's it like, being such a powerful woman in a male-dominated sector? What's your plan for Yahoo? What salary package did it take to lure you across from Google? How did the board react when you told them you were pregnant? How do you feel about working women, mothers and feminists celebrating your appointment as CEO? Can you hear the ground breaking beneath you, you wonderful thing? What will you do if you realise you need more maternity leave? What is your favourite flavour of cupcake?