Prince William & Catherine, Duchess of Cambridge, Leave The King Edward VII Hospital

Prince WiIliam, the Duke of Cambridge (L) and his wife Catherine the Duchess of Cambridge leave the King Edward VII hospital in central London, on December 6, 2012. Prince William's pregnant wife Catherine left a London hospital four days after she was admitted for treatment for acute morning sickness, an AFP photographer said (credit: LEON NEAL/AFP/Getty Images)

Duchess Of Cambridge Leaves The King Edwards VII Hospital

The Duchess of Cambridge, Catherine Middleton and Prince William, Duke of Cambridge leave the King Edward VII hospital where she has been treated for hyperemesis gravidarum, extreme morning sickness at King Edward VII Hospital on December 6, 2012 in London, England. (credit: LEON NEAL/AFP/Getty Images)

Prince William & Catherine, Duchess of Cambridge, Leave The King Edward VII Hospital

Britain's Prince WiIliam, the Duke of Cambridge, (L) and his wife Catherine, Duchess of Cambridge, leave the King Edward VII hospital in central London, on December 6, 2012. Prince William's pregnant wife Catherine left a London hospital on Thursday, four days after she was admitted for treatment for acute morning sickness.(credit: LEON NEAL/AFP/Getty Images)

Prince William & Catherine, Duchess of Cambridge, Leave The King Edward VII Hospital

Britain's Catherine, Duchess of Cambridge, wife of Prince WiIliam, leaves the King Edward VII hospital in central London, on December 6, 2012. Prince William's pregnant wife Catherine left a London hospital on Thursday, four days after she was admitted for treatment for acute morning sickness. (credit: LEON NEAL/AFP/Getty Images)

Prince William & Catherine, Duchess of Cambridge, Leave The King Edward VII Hospital

Britain's Catherine, Duchess of Cambridge, wife of Prince WiIliam, leaves the King Edward VII hospital in central London, on December 6, 2012. Prince William's pregnant wife Catherine left a London hospital on Thursday, four days after she was admitted for treatment for acute morning sickness. (credit: LEON NEAL/AFP/Getty Images)

Prince William & Catherine, Duchess of Cambridge, Leave The King Edward VII Hospital

Britain's Catherine, Duchess of Cambridge, wife of Prince WiIliam, leaves the King Edward VII hospital in central London, on December 6, 2012. Prince William's pregnant wife Catherine left a London hospital on Thursday, four days after she was admitted for treatment for acute morning sickness.

Prince William & Catherine, Duchess of Cambridge, Leave The King Edward VII Hospital

Britain's Prince WiIliam, the Duke of Cambridge, (L) and his wife Catherine, Duchess of Cambridge, leave the King Edward VII hospital in central London, on December 6, 2012. Prince William's pregnant wife Catherine left a London hospital on Thursday, four days after she was admitted for treatment for acute morning sickness. (credit: LEON NEAL/AFP/Getty Images)

Prince William & Catherine, Duchess of Cambridge, Leave The King Edward VII Hospital

Britain's Prince WiIliam, the Duke of Cambridge, (L) poses for pictures with his wife Catherine, Duchess of Cambridge, as they leave the King Edward VII hospital in central London, on December 6, 2012. Prince William's pregnant wife Catherine left a London hospital on Thursday, four days after she was admitted for treatment for acute morning sickness. (credit: LEON NEAL/AFP/Getty Images)