Kate Middleton's pregnancy was confirmed by St. James's Palace Monday morning, E! News reported.
"Their Royal Highnesses the Duke and Duchess of Cambridge are very pleased to announce that the Duchess of Cambridge is expecting a baby," E! News reported the palace said.
Middleton was admitted to King Edward VII Hospital in London after suffering from morning sickness, New York Daily News reported.
Middleton will remain hospitalized for a few more days "and will require a period of rest thereafter," New York Daily News reported the palace said.
Although an expected due date has not yet been announced, E! News reported that Middleton is still in the very early stages of pregnancy.
"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 palace said.