U.K. bookmaker are taking bets on whether the royal arrival will be a boy or a girl, with the latter being the odds-on favorite.
The baby's sex could be crucial, according to one retail expert, who said it could determine the extent of the "baby boom" for the U.K. economy.
Joshua Bamfield, director of the U.K.'s Centre for Retail Research, told CNBC he expected the new arrival to bring a short-term boost to the U.K. economy of around £80 million ($120.4 million).
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"I think there will be an immediate boost of around £80 million when the baby is born, with around £20 to £35 million spent on souvenirs and such like," Bamfield told CNBC, although he stressed that the excitement surrounding this baby was unlikely to reach levels seen when Prince George was born in July, 2013.
"If the weather is good…then we could expect more money to be spent on food and drink, as people have barbecues too," he added.
However, if the baby is a girl, the longer-term boost could be "quite significant," Bamfield argued, with the retail and fashion industries set to benefit in particular.
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"If the baby is a girl, you can imagine how images of her are going to be pored over from the minute go -- to see what she's wearing, what brands Kate and William have dressed her in," he said.
"Right up to when she's older and attending proms or balls, she will be getting a lot of media attention in terms of fashion."