The statement from Kensington Palace also offered a health update regarding the mom-to-be. "As with her first pregnancy, The Duchess is suffering from Hyperemesis Gravidarum. Her Royal Highness will no longer accompany The Duke of Cambridge on their planned engagement in Oxford today. The Duchess is being treated by doctors at Kensington Palace."
Monday's royal baby news is sure to cause some other rescheduling with the Duchess' public appearances. She is to have a two-day visit to Malta later this month, and is supposed to join her brother-in-law Prince Harry at the Invictus Games this week.
Kate is thought to be fewer than three months along in her pregnancy.
Third in line to the throne, Prince George was born on July 22, 2013 and has been at the center of an adorable media frenzy even before he was taking his first steps. George and his soon-to-be-sibling will be about the same age difference as Prince Harry and William.