The most vital question, though, is the baby's name. In mid-April, said Adams, "Alexandra" -- Queen Elizabeth's middle name, Queen Victoria's real name and the name of King Edward VII wife -- was all the rage.
"Over a 48-hour period, we took over 400 bets over Alexandra," said Adams.
While other popular guesses include Elizabeth, Diana and Mary, others are a little more creative.
Jessica Bridge, a spokesperson for Ladbrokes, another large U.K. bookmaker, said that in December her company received a 10-pound wager for the baby to be called, "Rylan" at 1,000-1 odds.
"Not sure the royal couple are 'X Factor' fans," she said.
Carole (25-1 odds), Phillipa (20-1), Spencer (33-1) and Oliver (33-1) were other possibilities.
In 1982, William Hill paid out nearly 30,000 pounds when Prince Charles and Princess Diana named their first child William. Bridge predicted the payouts will be even bigger this time around.
"This is certainly the biggest novelty event in history," she said. "Kate and Wills are even bigger than Charles and Diana. They've really captured the hearts and imaginations of people around the world. I think it's because they're this young couple and sort of normal. William has a job, Kate has a job. We can relate to them, even though they are the Duke and Duchess of Cambridge. They're not stuffy and boring."
Though Americans might be able to relate to them, they are not allowed to bet on them in the United States.
"In the U.K., they have been doing these types of things for a long time; you can bet on virtually anything," said A.G. Burnett, chairman of the Nevada State Gaming Control Board. "Here, historically and culturally, we look at it from a different perspective. Aside from casino-style games, we really only have sports wagering and that's a fairly highly regulated activity.
"Someday, we might go down that path, but it's just not been something of high demand for us," he added.
Still, that doesn't prevent others from betting on American, er, "royalty": Kim Kardashian and Kanye West and their forthcoming child. According to Bridge, the shortlist of potential baby names includes Krystal (10-1), followed by Kirsten (12-1) and Kara (14-1).
There's a 25-1 change they'll name it Kate or Katherine, but that is unlikely, she said.
One thing was clear, however: "It's an absolute given that Kimye's baby girl will have a name beginning with K," she said. "The list of names is endless, but Krystal Kardashian-West has a nice ring to it."