Wedding fever gripped the UK as royal-watchers and the general public speculated for months about what Catherine would wear, her hair and the scale of the event in a country entrenched in austerity measures.

Street parties were planned and a myriad of royal memorabilia lined shelves as the country prepared for an influx of visitors.

Then finally, on April 29, 2011, Catherine married Prince William in a televised ceremony at Westminster Abbey in London, becoming Her Royal Highness the Duchess of Cambridge, before an audience of millions.

Read more: Wedding Special | British royal family tree

In January 2012, the duchess announced the four charities she would support as a patron: the Art Room, which helps disadvantaged children express themselves through art; the National Portrait Gallery, which houses a famous collection of royal paintings and photographs; East Anglia's Children's Hospices, which helps children with life-threatening conditions; and Action on Addiction, which assists those with addiction issues.

Since then, the duchess has braved her first public speech and traveled with her new husband to meet royal supporters in Canada and more recently in Southeast Asia.

The latter was marred by controversy over a decision by a French magazine to publish images of the duchess sunbathing topless while on a private holiday with William in France. The couple took legal action action the magazine, French Closer, in September, which was also fined by a French court and ordered not to distribute the edition in print or online. It was also told to hand over the photos to the royals within 24 hours.

The Duchess of Cambridge was last seen in public during an official tour to Cambridge, England last week, when there was more talk about her new hairstyle than any speculation of pregnancy.

The palace has declined to name a due date, as Catherine is less than 12 weeks pregnant. She's expected to remain in hospital for several days while doctors treat her for Hyperemesis Gravidarum, a condition that causes acute morning sickness.

Prince William and Catherine's child will be next in line to the throne after William regardless of whether it is a boy or a girl, the British Cabinet Office said Monday. Last year, Commonwealth leaders agreed to change British succession laws to allow a female to take the throne ahead of a younger brother.