The Duchess of Cambridge is due to give birth in April 2015, it was announced today (20 October) in a tweet from Clarence House.
Kate's due date has been a subject of intense speculation since it was announced last month that the royal couple were expecting a brother or sister for Prince George.
"Their Royal Highnesses The Duke and Duchess of Cambridge are delighted to confirm they are expecting a baby in April 2015," read the statement from Clarence House, without giving a specific date.
The announcement of the due date indicates that Kate has already had her 12-week scan. Last week, photos emerged purportedly showing the Duke and Duchess leaving a London hospital after undergoing the scan.
The pictures are believed to show the Duchess carrying a brown envelope believed to contain sonogram images.
Palace officials were reportedly furious over the press intrusion - a sensitive topic for the royal couple - and the photos were not published in the UK, although they appeared in US publications.
Clarence House officials also commented on Kate's health in this morning's statement. There has been concern for the Duchess, who suffered hyperemesis gravidarum during her first pregnancy and has been struck down by the condition again.
"The Duchess of Cambridge continues to be affected by Hyperemesis Gravidarum, but her condition is steadily improving," the palace commented.
Her illness, a form of extreme pregnancy sickness, has forced her to cancel a string of engagements over the last six weeks, including a solo visit to Malta which was undertaken by Prince William instead.
The news of her improving health means that she is likely to resume her official duties tomorrow (21 October), when she and Prince William are scheduled to greet the President of Singapore and his wife, who are in London on a state visit.