Kate and Wills could be expecting TWINS, it emerged today.
Mothers-to-be who suffer from the hyperemesis gravidarum condition are three times more likely to have a multiple birth than other women.
William returned to Kate's bedside at 11.30am after his pregnant wife began a second day in hospital battling the severe morning sickness.
The Duchess, who is under 12 weeks pregnant, is expected to remain at the private King Edward VII hospital in central London for several days.
Wills and Kate had been hoping to keep the news they were expecting a baby secret until Christmas Day, it was reported.
But they were forced to make the announcement after she was admitted to hospital.
Kate was on a drip in hospital last night after suffering severe vomiting since the weekend. She is likely to be kept in for several days as a precaution.
Doctors at central London’s King Edward VII hospital in Marylebone will replace lost fluids to keep dehydration at bay, boost her nutrition and monitor her progress.
Sources said the couple initially had “no plans whatsoever” to announce the pregnancy until after she had had her 12-week scan, it was reported.
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 Kate’s arrival at hospital yesterday forced Palace officials to make the unplanned announcement.
Reports claimed she was barely eight weeks pregnant while the Palace confirmed she was less than 12 weeks pregnant — the earliest point at which a birth is usually announced.
Even the Queen and other senior Royals were taken by surprise because Kate and Prince William had not yet broken the news.
It is not yet known when the baby is due but Kate is believed to have found out she was expecting in the past four weeks.
A Royal source said: “William and Catherine are very happy but understandably nervous given her illness.
“They weren’t expecting to announce this so soon but once it was clear the Duchess had to spend several days in hospital it became clear the news would leak out.”
Palace officials confirmed Kate has the acute morning sickness known as hyperemesis gravidarum.
Kate and Wills’ baby will be third in line to the throne — and eventually King or Queen.