LONDON — The most widely anticipated pregnancy since Princess Diana's in 1981 is official: Prince William's wife, Kate, is pregnant.
St. James's Palace announced the pregnancy Monday, saying that the Duchess of Cambridge — formerly known as Kate Middleton — has a severe form of morning sickness and is currently in a London hospital. William is at his wife's side.
News of the pregnancy drew congratulations from across the world, with the hashtag "royalbaby" trending globally on Twitter.
The couple's first child will be third in line to take the throne — leapfrogging the gregarious Prince Harry and possibly setting up the first scenario in which a U.K. female heir could benefit from new gender rules about succession.
The palace would not say how far along the 30-year-old duchess is, only that she has not yet reached the 12-week mark. Palace officials said the duchess was hospitalized with hyperemesis gravidarum, a potentially dangerous type of morning sickness where vomiting is so severe no food or liquid can be kept down. They said she was expected to remain hospitalized for several days and would require a period of rest afterward.
"The best advice for anyone suffering from (severe morning sickness) is to get plenty of rest and drink lots of fluid," Dr. Daghni Rajasingam, a spokeswoman for Britain's Royal College of Obstetricians and Gynaecologists, said in a statement. "The condition usually subsides by week 12 of the pregnancy and with early diagnosis and treatment, there is no reason why we shouldn't expect a healthy pregnancy."
The condition is thought to affect about one in 200 pregnant women, according to Britain's health department.
The news came just days after the duchess, on a royal appearance, played field hockey with children at her former school.
Not only are the attractive young couple popular — with William's easy common touch reminding many of his mother, the late Diana — but their child is expected to play an important role in British national life for decades to come.
William is second in line to the throne after his father, Prince Charles, so the couple's first child would normally become a monarch — eventually.
The confirmation of Kate's pregnancy caps a jam-packed year of highs and lows for the young royals, who were married in a lavish ceremony at Westminster Abbey last year.
They have traveled the world extensively as part of Queen Elizabeth II's Diamond Jubilee celebrations and weathered the embarrassment of a nude photos scandal, after a tabloid published topless images of the duchess.
Joe Little, managing editor of Majesty magazine, said the news bookended a year that saw the royal family riding high in popular esteem after celebrations of Queen Elizabeth II's 60 years on the throne.
"We're riding on a royal high at the moment at the end of the Diamond Jubilee year," he said. "People enjoyed the royal romance last year and now there's this. It's just a good news story amid all the doom and gloom."
Speculation about when the couple would start a family has been rife since their wedding.