Kate Middleton, now the Duchess of Cambridge, is pregnant, Britain's royal family has announced.
The Queen and Duke of Edinburgh, the Prince of Wales and members of both families are delighted with the news, said a spokesman.
But St James’s Palace said in a statement that Kate had been admitted to a private hospital for treatment for a severe form of morning sickness known as hyperemesis gravidarum.
St James’s Palace said in the statement: “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.”
Speculation the duchess could be pregnant was sparked last week when on a visit to Cambridge, William accepted a gift of a babygro with 'Daddy's little co-pilot' and a picture of a helicopter on it from new mother Samantha Hill, the motif is a reference to William's RAF search and rescue pilot career.
It had also been speculated the prince will step down from his role as a search and rescue pilot, to return to the Household Cavalry to allow him to move back to London and free up more of his time.
There was speculation too that the Duchess, who showed herself to be at ease with youngsters on official engagements, was broody.
Even the food they had shipped to their honeymoon island in the Seychelles - apparently Brussels sprouts – led to suggestion Kate was on a fertility diet aimed at boosting her intake of folic acid.
There will be much excitement among the couple’s families.
The baby will be Carole and Michael Middleton’s first grandchild and the first for the Prince of Wales.
The new baby will be born third in line to the throne and in direct succession to the throne. The child will one day be head of the armed forces, supreme governor of the Church of England and head of the Commonwealth, which covers 54 nations across the world, and subsequently head of state of 16 countries.
The birth will also expose the couple to a new level of public fascination.
With the world ready to watch their baby grow up, William and Kate will have to balance protecting their prince of princess with the nation’s avid interest in its future king or queen.
When William was born, thousands of people gathered outside Buckingham Palace to wait for the birth to be formally announced.
He was the first future British king to be born in a hospital, delivered at the private Lindo Wing of St Mary’s Hospital in Paddington, London.
The newborn Prince arrived in June 1982 just under a year after his parents’ marriage, while the Queen had Charles in a similar timescale.