The Kate Middleton lookbook

Prince William, the Duke of Cambridge and Kate, the Duchess of Cambridge tour the Cloud Forest at Singapore's Gardens by the Bay on Wednesday Sept. 12, 2012. The palace confirmed Monday that the Duchess is pregnant, and she is hospitalized due to extreme morning sickness. (AP Photo/Wong Maye-E/Pool)

She's the world's most stylish mum-to-be.

On Monday, the palace announced the Duchess of Cambridge is expecting her first child with her husband, Prince William. Before the world's most fashionable royal child is born, we take a look at the sartorial selections of Kate Middleton, who topped multiple best-dressed lists including Vanity Fair's International Best-Dressed List of 2012.

The 30-year-old is so influential with her clothing that a retail term has been created after her dubbed, "The Kate Middleton Effect," which basically implies that she drives retail sales like no other celebrity or royalin the world. Take a look at her classic, well-tailored pieces, below.