In fact, one confident punter from Edinburgh has staked £2,000 on the newborn being female.
The Duchess is due to give birth towards the end of April, and plans to have her baby in the private Lindo Wing of St Mary's Hospital, Paddington, where Prince George was born in July 2013. And although Kate and Prince William have said they have no idea whether they're having a brother or sister for Prince George, bookies have slashed odds on the baby being a girl.
Odds started out being equal for a boy or a girl, but a girl is now the 8/13 favourite with a boy being 6/5.
Ladbrokes, which took the £2,000 bet on a girl – its largest bet to date on the royal baby, said nine in 10 bets on the baby's sex were being placed on a girl, a statistic that is being repeated in other bookmakers around the country.
Jessica Bridge, spokesman for Ladbrokes, told the Telegraph: "Money talks, and punters all over the UK are convinced Kate will give birth to a baby girl soon. It looks like the only people hoping for a boy are the bookies, and maybe Prince George."
If the Royal baby is a girl, Alice is still the favourite name, with odds of 3/1, followed by Elizabeth, Charlotte, Alexandra and Victoria.
For a boy, James is the 8/1 favourite, followed by Arthur, Henry and Charles.
However, speculation has also mounted that the baby could be named Sam, regardless of its gender, after the Royal couple's jockey friend, Sam Waley-Cohen.
For more odds on the Royal baby click here.
More:Pregnancy Week By Week
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