The Duke and Duchess of Cambridge have confirmed that their second child is due in April next year, Kensington Palace has said.
A statement from the palace said Kate is still being affected by hyperemisis gravidarum - a complication of pregnancy which causes vomiting and nausea - but her condition is said to be "improving".
"Their Royal Highnesses The Duke and Duchess of Cambridge are delighted to confirm they are expecting a baby in April 2015," it read.
"The Duchess of Cambridge continues to be affected by hyperemesis gravidarum, but her condition is steadily improving."
She had to cancel a series of engagements after her pregnancy was announced on September 8 because of the condition, which she also suffered during her pregnancy with son George.
The confirmation could suggest that Kate has had her 12-week scan. The baby could therefore be due around the end of April, and could even arrive around William and Kate's fourth wedding anniversary on April 29.
The Prince of Wales and the Duchess of Cornwall also celebrate their tenth wedding anniversary on April 9.
Kate's last official appearance was more than two months ago on August 5 at the Tower of London poppy exhibition.
She has been splitting her time between Kensington Palace and her parents' home in Bucklebury, Berkshire while struggling to cope with her severe morning sickness.
The announcement that the couple are expecting their second child came two months after Prince George turned one. The third-in-line to the throne was born on July 22 last year to a worldwide fanfare.
There will be around 21 months between Prince George and his new brother or sister, a similar age gap between Kate and her younger sister Pippa.