Prince William's wife checked into the private King Edward VII Hospital in London with debilitating condition hyperemesis gravidarum shortly before the couple revealed their baby news to the world on Monday (03Dec12).
After spending the last three days under medical supervision, the royal left hospital on Thursday morning (06Nov12).
The Duchess, looking pale and tired and clutching a bunch of yellow roses, was escorted to a waiting car by her husband.
Despite her bout of ill health, she managed to smile for photographers and told reporters she was feeling ""much better"".
Catherine will now recover at Kensington Palace, the couple's royal residence in London.
A St James's Palace spokesman says, ""The Duchess of Cambridge has been discharged from the King Edward VII Hospital and will now head to Kensington Palace for a period of rest. Their Royal Highnesses would like to thank the staff at the hospital for the care and treatment the Duchess has received.""
The Duchess' departure comes two days after a headline-grabbing prank by Australian radio hosts Mel Greig and Michael Christian, who phoned the hospital pretending to be members of Britain's royal family.
They were put through to Catherine's private nurse who gave them personal information relating to the royal's condition.
Bosses at the hospital have since apologised for confidentiality breach.