LONDON: Prince William’s wife Catherine on Monday spent the night in hospital where she is being treated for acute morning sickness following the announcement that the couple are expecting their first child.

The family revealed the news earlier Monday, ending fevered speculation about a baby destined to become Britain’s monarch whether it is a boy or a girl.

But Saint James’ Palace also revealed that the former Kate Middleton, 30, was in hospital suffering from “hyperemesis gravidarum.”

Queen Elizabeth II and the rest of the royal family were “delighted” by the news of the pregnancy while William—the son of the late Princess Diana and the heir to the throne Prince Charles—had visited her in hospital, the palace said.

The pregnancy adds to resurgent support for the monarchy after the pomp of William and Catherine’s wedding in April 2011 and the Diamond Jubilee celebrations to mark the queen’s 60th year on the throne in June this year.

“Their Royal Highnesses The Duke and Duchess of Cambridge are very pleased to announce that The Duchess of Cambridge is expecting a baby,” Saint James’ Palace said in a statement, using the couple’s official titles.

The baby is set to be third in line to the British throne after Charles and William, irrespective of its gender, following moves by the government to change ancient succession laws giving priority to male children.

The palace said the couple were only “recently” aware that Catherine was pregnant. The Press Association reported that the pregnancy has not passed the 12-week point and that the announcement was prompted by her medical condition.

The palace said Catherine was admitted on Monday to the King Edward VII Hospital in central London with hyperemesis gravidarum, which it defined as “very acute morning sickness”, which requires extra hydration and nutrients.

“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,” the statement said.

The queen, her husband Prince Philip, William’s father Prince Charles, Charles’s wife Camilla, William’s brother Prince Harry “and members of both families are delighted with the news,” the palace said.

Prime Minister David Cameron said the royal couple would make “wonderful parents” and that “people round the country will be celebrating with them tonight.”

William’s uncle Earl Charles Spencer—the brother of Diana who won praise for his emotional eulogy at her funeral after she died in a car crash in Paris in 1997—said he was “thrilled for them both”.