Princess Kate is expecting her second child.
"Their Royal Highnesses The Duke and Duchess of Cambridge are very pleased to announce that The Duchess of Cambridge is expecting their second child," said the official announcement Monday morning.
"The Queen and members of both families are delighted with the news."
"The Duchess is being treated by doctors at Kensington Palace."
Kate and Prince William, both 32, welcomed son George in July 2013, and from the moment he was born, the third in line to the throne has captivated royal-watchers around the world.
From his first play date to learning how to walk, the red-headed toddler – who William calls "a little rascal" – has kept his proud parents on their toes.
As for the arrival of his sibling, Kate is believed to be fewer than three months pregnant.
When she was carrying Prince George, she was admitted to the hospital suffering from the same illness before she was eight weeks along.
Monday's announcement came, in part, as a result of her having to pull out of that day's appearance in Oxford with William Monday. The Palace is now reviewing her upcoming engagements, including her two-day visit to Malta scheduled for later this month.
She was also due to join William at brother-in-law Prince Harry's Invictus Games later this week.
• Reporting by SIMON PERRY