Kate Middleton's Hospital Falls for Prank Call From Australian Radio Station

Dec. 5, 2012— -- The hospital where Kate Middleton is battling acute nausea fell for a prank call from an Australian radio show, revealing to the royal impersonators that Kate is "quite stable" and hasn't "had any retching."

Today is the pregnant duchess's third day at London's King Edward VII Hospital, where she is undergoing treatment for hyperemesis gravidarum -- severe or debilitating nausea and vomiting. Prince William and her sister Pippa Middleton both visited her in the hospital today.

The hospital inadvertently revealed new details about Kate's condition when Australian DJ's Mel Greig and Michael Christian called in and pretended to be Queen Elizabeth II and Prince Charles, complete with exaggerated accents. They even enlisted two co-workers to bark like the queen's corgis.

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The queen impersonator asked for her granddaughter and was promptly transferred to another hospital employee.

"I'm just after my granddaughter, Kate. I want to see how her little tummy bug is going," the radio host said, suppressing laughter.

"She's sleeping at the moment, and she has had an uneventful night and sleep is good for her," the nurse said. "She's been getting some fluids to rehydrate her because she was quite dehydrated when she came in, but she's stable at the moment."

The fake royals went on to ask when would be a good time to visit and were told that "anytime after 9 o'clock would be suitable."

"She's quite stable at the moment. She hasn't had any retching ... since I've been on duty. And she has been sleeping on and off. I think it's difficult sleeping in a strange bed as well," the nurse said with a laugh.

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The hospital confirmed today that the call happened early Tuesday morning.

"The call was transferred through to a ward, and a short conversation was held with one of the nursing staff," the hospital said in a statement. "King Edward VII's Hospital deeply regrets this incident."

"This was a foolish prank call that we all deplore," John Lofthouse, the hospital's chief executive, said in the statement. "We take patient confidentiality extremely seriously, and we are now reviewing our telephone protocols."

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The radio station has since apologized for the prank call.

"2Day FM sincerely apologizes for any inconvenience caused by the inquiry to Kate's hospital. The radio segment was done with lighthearted intentions," the station said in a statement.

"We were very surprised that our call was put through. We thought we'd be hung up on as soon as they heard our terrible accents," the radio hosts said in the statement. "We're very sorry if we've caused any issues, and we're glad to hear that Kate is doing well. We wish Kate and her family all the best."

Hyperemesis gravidarum, or acute nausea, is usually diagnosed about nine weeks into a pregnancy, and in most cases resolves itself by 16 or 20 weeks, according to Dr. Ashley Roman, a professor and obstetrician-gynecologist at New York University Langone Medical Center. In rare cases, it can last the whole pregnancy.

The Sun reports that Prince Harry sent Kate an email from his post at Camp Bastion in Afghanistan, telling her to "Get well soon, Sis."

Kate will be in the hospital for 'several days," and will then require a "period of rest," Clarence House said Monday.

"There's been an outpouring of support for the couple that made them feel, perhaps, a little bit more positive about the whole thing," said Victoria Murphy, a royal correspondent with the Daily Mirror.

William left King Edward VII Hospital at around 5:45 p.m. local time Tuesday after spending more than six hours at Kate's bedside. He appeared more relaxed than he did Monday, when Kate was admitted.

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"The Duchess of Cambridge is continuing to feel better," a St. James Palace spokesman said Monday. "She and the duke are immensely grateful for the good wishes they have received. She will remain in hospital at present and will continue to be treated for hyperemesis gravidarum."

William can relax, as Kate seems to be in good hands -- she is reportedly being treated by the queen's doctors. The couple is set to move into a newly renovated Kensington Palace early next year, which might make the pregnancy easier.

Kate's parents, Carole and Michael Middleton, were spotted leaving their home in Bucklebury Tuesday. They will reportedly make the 50-mile trek to London to visit their daughter. Other than William, no other member of the royal family has been spotted entering or leaving the hospital.

Speculation is still in overdrive on exactly how far along the pregnancy is, as the palace would not comment.

"The royal family would not normally want to announce a pregnancy before the 12-week mark, and we understand it's quite a substantial way before the 12-week mark," said Murphy. "We believe she's about seven to eight weeks pregnant at the moment."

ABC News' Sydney Lupkin, Carolyn Durand, Amanda Keegan and Kelly Hagan contributed to this report.