The royal baby could share the same birthday as Princess Diana or Camilla, Duchess of Cornwall. St James’s Palace has announced that the Duchess of Cambridge’s baby is due in July.
Speculation is rife over possible names for the baby and the timing of the birth could provide a clue.
For instance, 1 July was the day William's mother was born - although Diana is likely to be a controversial choice within the royal family.
His stepmother Camilla, Duchess of Cornwall, celebrates her birthday on 17 July.
Elizabeth could be a popular choice if the new royal baby, who will be third in line to the throne, if it is a girl - especially as the summer will mark the 60th anniversary of the Queen’s coronation.
The gates to the grounds of Buckingham palace are being opened between 11 and 14 July to celebrate the landmark.
Other notable possible dates include the birthday of Nelson Mandela, one of the Prince's idols, Beatles Day (John, Paul?), Bastille Day (Frances?) and Wimbledon (Andrew?).
In December, the Duchess of Cambridge announced the news that she was pregnant earlier than she had hoped because she is suffering from Hyperemesis Gravidarum, or severe morning sickness.
Once it was became clear that she would have to spend a couple of days in hospital, royal aides decided the news could not be kept secret any longer, even though she has not yet had her three month scan.
Most parents to be prefer waiting for the results of the scan before informing even close family and reports suggest the Duchess was planning to wait until Christmas before revealing the news.
Key possible due dates:
1 July: Diana, Princess of Wales' birthday
3 July: Henley Regatta
7 July: Men's singles final at Wimbledon
9 July: Hampton Court Flower Show begins
10 July: Beatles Day
14 July: Bastille Day
15 July: River Thames swan census
17 July: Camilla, Duchess of Cornwall’s birthday
18 July: Nelson Mandela’s birthday