Prince William and Kate announced on Monday that they are expecting their first child, due next year.

The Royal couple were forced to reveal their pregnancy earlier than planned after the Duchess was admitted to the King Edward VII Hospital in London on Monday after feeling unwell at the weekend while staying with her parents in Bucklebury, Berkshire.

Karen Wolfe, head matron for Women and Children’s Services at Ipswich Hospital, said the condition, hyperemesis gravidarum, doesn’t pose a risk to the unborn baby but in severe cases it can cause nutrition problems, as with other severe illnesses.

“Morning sickness, hyperemesis gravidarum, is caused by the release of the pregnancy hormone called human chorionic gonadotropin (HCG),” she said.

“All pregnant women release the hormone, but some have a much stronger reaction to others and may need a short admission to hospital for rehydration and anti-sickness medications to control excessive vomiting.

“Here at Ipswich we can go several weeks without any women being admitted with Hyperemesis gravidarum, but sometimes there will be three or four women being cared for this condition at one time.”

It is likely her symptoms of severe vomiting may last for much of her pregnancy.