According to reports, the Duchess of Cambridge, who is expecting her first child with Prince William, maybe pregnant with twins.
Kate, who has been admitted to the King Edward VII Hospital in London after she got ill while staying with her parents in Bucklebury, Berkshire, is suffering from hyperemesis gravidarum, a condition that is more often experienced by women expecting twins, the Telegraph reported.
Mothers-to-be who suffer from the condition are three times more likely to have a multiple birth than other women.
She is expected to remain there for several days.
Prince William spent Monday at her bedside. He was seen leaving the hospital at 8.20pm and is expected to be granted compassionate leave from his RAF Search and Rescue duties.
The Duchess's illness prompted a scramble to tell members of the Royal family about the pregnancy before news of her arrival at hospital leaked out.
Royal aides said the decision to go public "was very much driven by the Duke and Duchess", who were aware that it would be impossible to keep the news a secret in the age of Twitter.
"It's a very hard thing to go public at such an early stage, but they wanted to be open with people as much as possible," an aide said.
Kate's illness, which affects fewer than four in every 1,000 pregnant women, causes severe vomiting and can lead to dehydration.
It is treated by giving fluids intravenously and by anti-sickness tablets but can last for months.