Kate, Britain's Princess of Wales, is being treated in hospital after undergoing successful abdominal surgery, Kensington Palace has announced.
The 42-year-old was admitted to The London Clinic yesterday for the planned procedure.
The future Queen is expected to remain in hospital for up to two weeks before returning home to continue her recovery.
The princess is not expected to return to public duties until after Easter based on current medical advice, the palace said.
A spokesperson said: "The Princess of Wales appreciates the interest this statement will generate.
"She hopes that the public will understand her desire to maintain as much normality for her children as possible; and her wish that her personal medical information remains private.
"Kensington Palace will, therefore, only provide updates on Her Royal Highness' progress when there is significant new information to share.
"The Princess of Wales wishes to apologise to all those concerned for the fact that she has to postpone her upcoming engagements.
"She looks forward to reinstating as many as possible, as soon as possible."
Meanwhile, Britain's King Charles will attend hospital next week to be treated for an enlarged prostate, Buckingham Palace said.
In a statement, it said: "In common with thousands of men each year, The King has sought treatment for an enlarged prostate.
"His Majesty's condition is benign and he will attend hospital next week for a corrective procedure.
"The King's public engagements will be postponed for a short period of recuperation."
It is understood the king was keen to share the details of his diagnosis to encourage other men who may be experiencing symptoms to get checked in line with public health advice.
He had a series of meetings and events planned at Dumfries House in East Ayrshire tomorrow and Friday, which are now being postponed on his doctor's advice.
Guests, including foreign dignitaries and members of the cabinet, were due to travel to Scotland and the palace made the announcement to allow for them to be made aware of the situation.
The 75-year-old monarch acceded to the throne just 16 months ago after spending 70 years as the heir to the throne, and was crowned last May in Westminster Abbey.
