As Woman's Day exclusively revealed, Kate is around two months pregnant and is due in March, 2018.
So for the next seven months, you can expect a lot of baby name and gender speculation.
And naturally, the bookies have already begun the guessing game.
"We're not sure who is more excited for the latest baby news – the royal couple or our punters. More stately names are no doubt the favourite, but we'd love to see a royal Wayne" sportsbet.com.au's Christian Jantzen told Now To Love.
Favourite girl names
If there's one thing we know for sure is that Wills and Kate will most definitely opt for a classic choice, drenched in history.
Their first-born son's full-name name is Prince George Alexander Louis of Cambridge, a nod to the Kings that came before him. While their daughter is Princess Charlotte Elizabeth Diana, in honour of The Queen and her late grandmother Princess Diana.
So far, the bookies firm favourite for a girl is tied between Alice and Victoria at $15 - both regal-sounding names with long-standing royal ties.
Alice was also a front-runner during the countdown to Princess Charlotte's birth in 2015. It was the name of one of Queen Victoria's daughter and Prince Philip's mother.
Mary and Alexandra come in for the second spot at $18.
In light of the 20-year anniversary of her death Sportsbet also predict another Princess Diana could be joining the history books, with a $30 chance.
Check out the full list below, via Sportsbet! Story continues after...
Favourite boy names
Can you imagine a Prince Henry of Cambridge? What about Prince Arthur?
Sportbet have their money on the above monikers for a baby boy, with both names at $15.
WATCH: Wills and Kate's sweetest parenting moments! Post continues below...
But given Prince Harry's full title is actually Prince Henry of Wales, Wills and Kate might be keen to mix it up.
Considering Prince Philip's recent retirement, it could be a touching tribute to the great grandfather to name their third child after him...
The full breakdown below! Article continues after...
Are Prince William and Duchess Catherine expecting a boy or a girl?
With their past two children, William and Kate haven't officially announced the genders of George and Charlotte until after the birth.
So we're guessing we won't know if we have a new Prince or Princess until baby Cambridge joins us next year.
At the moment, the bookies money is on another girl called Alice.
Meanwhile there's a 4/1 chance that it could be double the joy with twins and a 50/1 chance with triplets.
If we had to place a bet, our precious pennies would be on Princess Alice!
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