The Duchess of Cambridge's first pregnancy will inevitably be followed with just as much excitement and media attention as Princess Diana's.
The announcement of Princess Diana's pregnancy came on 5 November 1981 - a little over three months after her marriage to Prince Charles.
There was tremendous speculation about whether the Royal baby would be a boy or a girl - not least because only a boy would be in direct succession to the throne.
Following a change in succession rules in October 2011, Catherine and William's child will be the first British monarch to be born with an equal right to the throne regardless of whether they are a girl or boy.
The parents-to-be suffered a serious scare just 12 weeks into the pregnancy when Diana fell down a staircase at Sandringham.
After checking both mother and baby, the royal gynaecologist Sir George Pinker concluded that the foetus was uninjured, although Diana suffered severe bruising.
Princess Diana's biographies suggest she felt enormous pressure carrying a potential heir to the throne. She is said to have complained that "the whole world is watching my stomach".
Princess Diana remained active during her pregnancy and attending official engagements until just a few weeks before Prince William's birth.
On 13 June, just two weeks before giving birth, she was photographed watching her husband play polo.
At 9.03pm on 21 June 1982, Diana gave birth naturally to a healthy boy in the private wing of St. Mary’s Hospital in Paddington, London. A bulletin announced that the Royal baby weighed 7lb 1 1/2oz.
The press, which had been camped outside the hospital for days, harangued Prince Charles for news after he visited his wife and new son.
He told reporters that he was "relieved and delighted" but that it was a "shock to the system". He also asked them not to make too much noise because "sleep is badly needed in there".
Judging by their relationship with the press so far, Catherine and William may opt for a more private experience, however.
The world's press didn't have to wait long for its first glimpse of the young prince.
The day after his birth, Princess Diana and Prince Charles appeared outside the hospital holding the heir to the throne swaddled in a white blanket.
The news of Prince William's birth spread around the world quickly with many newspapers running the headline: 'It's a boy'.
The official proclamation of Prince William Arthur Philip Louis' birth came in the form of a notice displayed on the gates of Buckingham Palace.
It read: "Her Royal Highness The Princess of Wales was safely delivered of a son at 9:03pm today. Her Royal Highness and her child are both doing well."
Hundreds of well-wishers and reporters turned up to catch a glimpse of it and to take photographs.
This tradition is still followed today even though the birth will also be announced the official website of the Royal family.
The Royal Horse Artillery fired a 41-gun salute in Hyde Park to celebrate the birth of the baby boy, but elsewhere celebrations were more low key.
At the primary school in Tetbury, Gloucestershire - the town when Charles and Diana lived - children made congratulations cards.