Presenters from Sydney’s 2Day FM station, posing as Queen Elizabeth II and William’s father Prince Charles, apparently managed to get through to a nurse treating Kate, who said she had not experienced any recent “retching”.
The chief executive of the private King Edward VII hospital in London, where 30-year-old Kate was admitted on Monday, confirmed that a nurse discussed her condition but deplored the “foolish prank”.
John Lofthouse said the hospital took patient confidentiality extremely seriously and was now reviewing its telephone protocols.
A spokesman for William and Kate at St James’s Palace said it was aware of reports of a prank call but would not be making further comment.
Kate is suffering from hyperemesis gravidarum, a severe form of morning sickness that affects about one in 200 pregnant women.
News of her pregnancy has ended feverish speculation about a new royal heir that began immediately after her lavish wedding to Prince William in April 2011.
The baby will be third in line to the throne regardless of whether it is a girl or a boy, after a historic agreement among the 16 Commonwealth realms last year to end the centuries-old practice of male primogeniture.