The Duchess of Cambridge, who spent three nights in hospital being treated for hyperemesis gravidarum, took a turn for the worse as she spent the weekend at Kensington Palace.
Prince William pulled out of an official engagement at the British Military Tournament at Earl's Court, London, yesterday night, so he could look after his wife, the Daily Telegraph reported.
The news came amid a row over the apparent suicide of an Indian-origin nurse between the hospital that treated the Duchess and an Australian radio station that made a hoax call of which the nurse was a victim.
Kate, 30, had said she was feeling "much better" when she was discharged from hospital on Thursday morning, and on Saturday night was well enough for the Duke to feel able to attend an engagement at the Royal Albert Hall.
But at lunchtime yesterday, St James's Palace announced that the Duke would be "spending Sunday privately with the Duchess" instead of going to Earl's Court.
A St James's Palace spokesman said: "It is well known that hyperemesis gravidarum often recurs and, until further notice, to allow the Duchess a degree of privacy during her pregnancy, we do not intend to offer regular condition checks or advise of routine developments associated with it".
The Duchess's condition was not serious enough for her doctors to consider sending her back to hospital, but women with the condition can experience symptoms for months and need repeated hospital admissions.
The Duke is expected to stay by his wife's side until Thursday, as he had taken time off from his work as an RAF search and rescue pilot to carry out several engagements, the last of which is at the royal film performance of The Hobbit on Wednesday.
The Duke is thought to have also been allowed compassionate leave.
It seems certain the Duchess will miss the event, meaning she will not be seen in public until Christmas Day at the earliest, when the Royal family traditionally attend church at Sandringham.
At a charity tennis gala on Saturday, the Duke spoke about his wife's condition, telling a guest: "I don't know why they call it morning sickness --they should call it all-day and all-night sickness."
