Kate Middleton, Duchess of CambridgeKate Middleton At The Newcastle Civic Centre in November

Kate Middleton is pregnant with her and Prince William's first child. The news was announced by St James Palace today on behalf of the Duke and Duchess of Cambridge, who married in 2011.

According to ABC News, the child - whether a girl or boy - will eventually be heir to the British throne, according to new legislation awaiting final approval. The Duchess was admitted to King Edward VII Hospital on Monday (December 3, 2012) with hyperemesis gravidarum, an acute morning sickness that requires supplementary hydration and nutrients. "As the pregnancy is in its very early stages, Her Royal Highness is expected to stay in hospital for several days and will require a period of rest thereafter. Their Royal Highnesses The Duke and Duchess of Cambridge are very pleased to announce that The Duchess of Cambridge is expecting a baby," the palace said in a statement today. "The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall and Prince Harry and members of both families are delighted with the news." The couple have made no secret of their desire to have children, though 'Kate Middleton pregnant' headlines have been cropping up on a weekly basis since the couple married. 

Kate Middleton, Creative Industries ReceptionPrince William, Kate Middleton, Cambridge

Kate Middleton Has Become Something of a Fashion Icon Since Becoming the Duchess of Cambridge

The change in the rules of succession means the couple's first-born will likely become the heir to the throne. The heads of 16 Commonwealth countries agreed to a change so that first-born children of either gender can take the throne. The British Parliament must still amend existing law to make the succession change official. "Put simply, if the Duke and Duchess of Cambridge were to have a little girl, that girl would one day be our queen," British Prime Minister David Cameron told reporters in 2011. It's common for Royal babies to be born within one year of marriage - Princess Diana gave birth to Prince William just 11 months after her wedding to Prince Charles. 

William and Kate became the talk of the world's media in the lead up to their wedding at Westminster Abbey in April 2011, though it's likely they're going to do it all again over the next nine months or so. Of course, there's going to be speculation over the sex, speculation over the name, speculation of which colour they choose for the nursery. In 18 years, there's going to be speculation over which university the child goes to and eventually which career path they take. Oh and the little blighter is going to have Prince Harry as an uncle.

The Duchess is still in hospital in central London and is expected to stay there for a couple of days.

Watch David Cameron announcing plans for the Duke and Duchess' first child to take the throne: