It’s also a chance to make a lot of money off a newborn.

Last year’s wedding of Prince Harry and Ms. Markle — now the Duke and Duchess of Sussex — was popular with gamblers. There were guesses about her dress (Givenchy), his beard (intact) and the weather (lovely).

But there are far more bets on Baby Sussex, who will be seventh in line to the throne. At the bookmaker William Hill, wagers are expected to reach $1.3 million. Another bookmaker, Boyle Sports, is taking bets on categories like the baby’s godparents and weight.

That’s more action than for each of the baby’s three royal cousins — the children of Catherine, the Duchess of Cambridge, and Prince William, Prince Harry’s brother — who are third through fifth in the succession lineup.

On the BookMaker.eu website, odds favor the baby’s being born in the morning on a Sunday, said Angus Hamilton, an entertainment specialist for the sports betting platform, who remembers similar wagers being placed when Princess Diana was pregnant.

The betting market for royal babies is not enormous, Mr. Hamilton said. On BookMaker.eu, there is less than $100,000 in related wagers, compared with the $1 million in bets that the Oscars sometimes draw on the day of the ceremony.