After months of speculation, St James's Palace has announced the Royal couple are expecting their first child.
A spokesman said the Duchess has been admitted to King Edward VII Hospital in central London with acute morning sickness. She is expected to stay in hospital for several days.
The new arrival will be third in line to the throne and great grandchild to the Queen.
A statement on the couple's website read: "Their Royal Highnesses The Duke and Duchess of Cambridge are very pleased to announce that The Duchess of Cambridge is expecting a baby.
"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 Duchess was admitted this afternoon to King Edward VII Hospital in Central London with hyperemesis gravidarum.
PA
"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."
The happy news comes after months of speculation that the Duke and Duchess would soon be starting a family.
Most recently, Prince William accepted a gift of a personalised babygrow from a member of the public, telling her: "I'll keep that!"
Congratulations Wills and Kate!
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