'World descends on London' as Kate remains in hospital After Buckingham Palace confirmed that the Duke and Duchess of Cambridge are expecting a baby, Kate was admitted to a central London hospital where she'll spend the next few days getting over severe morning sickness. TODAY's Natalie Morales reports. Optimally, news of a pregnancy is kept under wraps until the end of the first trimester. But when Duchess Kate's morning sickness became so severe that it sent her to the hospital, it also sent Buckingham Palace officials to the media with an earlier-than-expected announcement. It then sent the media into a gleeful frenzy, with social media outlets buzzing about the newest heir to the British throne. "The world is already descending on London, and everyone has a huge smile on their faces," Ben Fogle, a friend of the royal couple, told TODAY from across the pond on Tuesday. The Duchess of Cambridge will stay for at least a second day at King Edward VII Hospital for treatment of hyperemesis gravidarum. The rare condition affects 2 percent of all pregnant mothers and causes severe nausea and vomiting. It often results in hospitalization because of concern over dehydration and the mother's inability to get proper nutrition. But the fetus is rarely affected by the condition, as long as the mother gets proper treatment and rest, NBC's chief medical editor, Dr. Nancy Snyderman, said on TODAY Tuesday. NBC's Dr. Nancy Snyderman discusses Duchess Kate's pregnancy and the acute form of morning sickness she's suffering from that causes dehydration and weight loss. "It usually starts about six to seven weeks into a pregnancy, and can go into 20 weeks, which is about five months," she said. I would suspect if she's this ill, this early, this is not going to be a 48-hour bout. The severity of her morning sickness has prompted speculation that Middleton may be carrying more than one child. "Could it be twins for Kate?" read the above-the-fold headline in Tuesday's Daily Telegraph. Women pregnant with twins are more likely to suffer from hyperemesis gravidarum because they have an elevated level of the pregnancy hormone that triggers the illness symptoms. Prince William, who returned to his wife's hospital bedside on Tuesday morning, will be savvy about how best to sate the world's interest in his wife's pregnancy, said royal expert Camilla Tominey. But he also will take measures to avoid the media circus that constantly surrounded his mother, the late Princess Diana, when she was pregnant with him. "I think the world has moved on a bit" since that period, Tominey said. I don't think anyone in this day and age is going to want to see a pregnant lady, or indeed a little baby, hounded, back to the Diana days. It will help that Prince William, who was born in 1982, grew up in the age of social media. NBC's Ben Fogle and royal expert Camilla Tominey weigh in whether Princess Kate's hospitalization affected the royal couple's decision to announce their pregnancy early and what kind of life Will and Kate and their baby can expect. Fogle said he, like the rest of the world, looks forward to watching developments unfold. "I can assure you that both William and Kate will be fantastic parents," he said. I think William will be very, very hands on, a real modern father. More: