Kate Middleton will remain in hospital for the next few days as a precaution, following the news that The Duke and Duchess of Cambridge are expecting their first child.
The couple stunned millions around the world, including their families, with the baby bombshell hours ago, while an anxious Prince William left hospital after his wife had been admitted suffering from acute morning sickness.
Barely eight weeks into her pregnancy, Kate, 30, was taken to the hospital just after lunch by her husband and immediately put on a drip to stop her becoming dehydrated.
Last night she appeared to be responding well to treatment and sources said there was "no cause for alarm".
However, doctors at the King Edward VII Hospital in central London have taken the precautionary step of keeping her in for the next few days.
It was a nerve-racking day for Prince William. He left the hospital in Marylebone last night wearing a grey jumper and blue shirt, but said nothing to the dozens of camera crews and photographers outside. He was then taken back to Kensington Palace by three royal protection officers in a green Land Rover.
The Duke had been at his wife's side for most of the day and royal sources confirmed he'll be back there today (local time).
The sources told the Daily Mail that the couple initially had "no plans whatsoever" to announce the pregnancy until after she had had her 12-week scan.
They also revealed that the Duke and Duchess had not planned to tell the Royal Family of their news until they were all gathered together at Sandringham at Christmas.
But in view of the Duchess's hospitalisation the couple made the "reluctant and difficult" decision to publicly confirm their news.
Members of the Royal Family - including the Queen and grandfather-to-be Prince Charles - were informed less than an hour before the statement was put out at 4pm yesterday.
Uncle-to-be Prince Harry, who is serving in Afghanistan, was told by email at his base and the announcement was also Tweeted by Clarence House, prompting the couple's official website to crash. All the family declared themselves to be "delighted" at the news.
However, it's believed Kate's parents, Michael and Carole Middleton, became aware of their daughter's news at the weekend. She was staying with them in Berkshire when her condition deteriorated.
Speculation that she may be pregnant began last week when she unveiled a head-turning new haircut with a parted fringe as she visited the National History Museum in London.
But the drama really began when Kate went to stay with her parents on Friday after a visit to her former preparatory school, St Andrew's, just a few minutes' drive away. At the time, she had appeared in good health, even taking to the hockey pitch in her high-heeled boots for a quick knock-about with students.
William had been spending the first part of the weekend privately with friends at a shooting party that Kate, for now obvious reasons, had declined to join. When he finally met up with his wife, however, he became increasingly concerned at her condition - particularly her inability to keep down any food or water.
On Monday afternoon, fearing she could become dehydrated which could prove a risk to both her and their baby, and after consulting their doctor by phone, he decided drive her to London in their Range Rover.
The couple declined the offer of an ambulance and drove themselves to the London hospital, where William's grandfather, Prince Philip, was hospitalised earlier this year.
By all accounts, the Duchess was in good spirits despite her condition and walked in unaided. Doctors diagnosed her with "hyperemesis gravidarum", a form of acute morning sickness, which was making her vomit "round the clock".
The palace said: "The Duchess was admitted this afternoon to King Edward VII Hospital in central London with hyperemesis gravidarum.
"As the pregnancy is in its very early stages, Her Royal Highness is expected to stay in hospital for several days and will require a period of rest thereafter."
Royal mothers are usually looked after by the Queen's gynaecologist - currently Alan Farthing, the former fiancé of murdered TV host Jill Dando.
The couple have made no secret of wanting to start a family. In an interview to mark their engagement, Kate, who is extremely close to her own parents and two siblings, revealed:
"I hope we will be able to have a happy family ourselves."
A spokesman for the couple said that they were not in a position to confirm how many weeks pregnant the Duchess is - except that the pregnancy was in its "very early stages".
But the Daily Mail understands Kate was not pregnant during the couple's tour of south-east Asia and the South Pacific in September.
The baby will be Prince Charles's first grandchild - he is already a doting grandpa to the Duchess of Cornwall's five grandchildren - and the Queen's third great-grandchild.
He or she will become third in line to the throne after Prince Charles and Prince William, making Prince Harry fourth.
- DAILY MAIL