Prince William and Kate expecting a baby:

It was announced overnight Australian time that Catherine, Duchess of Cambridge, and her husband Prince William, are expecting their first child.

The royal family are "delighted" by the news of the baby, who will the third in line to the British throne occupied by Queen Elizabeth II.

"Their Royal Highnesses The Duke and Duchess of Cambridge are very pleased to announce that The Duchess of Cambridge is expecting a baby," St James's Palace has announced.

"The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall and Prince Harry and members of both families are delighted with the news."

William, the son of heir to the throne Prince Charles and the late Princess Diana, married the former Kate Middleton in April last year and there has been intense speculation about when the couple, who are both 30, would have a baby.

The statement added: "The Duchess was admitted this afternoon to King Edward VII Hospital in central London with Hyperemesis Gravidarum (severe morning sickness).

"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."

Severe morning sickness is thought to be caused by hormonal changes during pregnancy and affects up to 3% of pregnant women. 

It is unpleasant - and can be downright miserable - for the mother but not threatening to her or the baby if treated appropriately including hospitalisation and the administering of intravenous liquids and nutrition.  

It usually starts with excessive vomiting in early pregnancy where a woman can struggle to keep anything down, even her own saliva. It generally begins between four and seven weeks and eases off between 14 to 16 weeks - which probably isn't much comfort to Kate at the moment. In most cases, it will end by the 20th week of pregnancy. Unfortunately, for around 20% of sufferers, it can last the entire pregnancy. Anti-sickness drugs have a good safety record and are unlikely to harm the baby.

There is evidence to suggest that hyperemesis gravidarum may be hereditary.