Updated: Kate Middleton is pregnant with her and Prince William's first child

Duchess of Cambridge and Prince William reveal they are expecting a baby

Kate Middleton and Prince William have today announced they are expecting a baby.

The Duchess of Cambridge is in the early stages of pregnancy, the palace revealed.

The Duke and Duchess of Cambridge at their most recent engagement in Cambridge © RexA spokesman for St James' Palace confirmed the news in a statement: "The Duke and Duchess of Cambridge are very pleased to announce that the Duchess of Cambridge is expecting a baby."

"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," the palace added.

[Related: Kate Middleton is suffering with hyperemesis gravidarum - what is it?

However, the statement also revealed that Kate had been admitted to a private hospital for treatment for a severe form of morning sickness known as hyperemesis gravidarum.

Kate Middleton is pregnant, a St James Palace has confirmed © RexSt 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."

It is unusual for a high profile (or any) pregnancy to be announced before 12 weeks but there has been speculation that Kate could be only around eight weeks pregnant. Rumour has it the couple had been keen to save their exciting news until Christmas Day but were forced to reveal the pregnancy after Kate fell ill.

Despite seeming on top form last week at the Natural History Museum and even playing a spot of hockey in heels at her former prep school, Kate developed this acute form of morning sickness over the weekend and was driven to hospital by William, where she has been put on a drip to prevent dehydration.

According to sources, Kate and Wills hadn't even had the chance to tell their close family, with many of the royal family finding out just an hour before the official statement was released. Prince Harry, who is currently serving in Afghanistan, was reached by email.

[Related: Kate Middleton makes headlines with her new sweeping fringe]

Kate and Wills' announcement follows weeks of speculation around whether the Duchess of Cambridge was indeed pregnant.

On a recent visit to Cambridge, William accepted a gift of a babygrow with 'Daddy's little co-pilot' from new mother Samantha Hill, the motif is a reference to William's RAF search and rescue pilot career.

The Prince was said to have been left blushing by the gift.Just last week Kate was in good health ©Rex

Kate will spend several days in hospital under medical supervision, but is said to be in good spirits and was able to walk unaided into hospital when she arrived. William, who has spoken in the past about his desire to be a dad, spent hours by her side and was photographed leaving the hospital yesterday evening.