Astrologers predict the royal baby will be "larger than life, charismatic and glamorous".
Duchess Catherine went into labour this morning (22.07.13) and is currently at the Lindo Wing of St. Mary's Hospital in Paddington, London.
With the duchess and Prince William's son or daughter due to arrive imminently, they will be on the cusp of two different star signs, Cancer and Leo, which astrologers say will play a part in determining the child's personality.
If the baby is born later today or tomorrow (23.07.13) it will be under the sign of Leo, but astrologer Patrick Arundell thinks it will still have very strong Cancerian traits.
He told the Daily Telegraph newspaper: "Either way, he or she is going to be larger than life, charismatic and glamorous but they will have a very Cancerian personality, whether under the sign of Leo or not, and be sensitive and caring.
"If the baby's born today it will have a slightly more conventional and conservative personality, but if it's born tomorrow it will be more groundbreaking and more in tune with modernity."
Patrick added the royal baby will have star quality due to the way the planets are aligned.
He added: "Mars and Jupiter are conjunct in Cancer and that will give the baby a tremendous amount of go-get energy and that is already in motion.
"Venus and the Sun are also in a magnetic connection which will give the baby a star quality and a sparkling charisma."
If the baby is born today he or she will share their birthday with Selena Gomez, Rhys Ifans and Willem Dafoe, if tomorrow the baby will share its birthday with Daniel Radcliffe, Woody Harrelson and the singer Michelle Williams.