Although Buckingham Palace has never confirmed the exact date, Saturday is rumored to be the official due date for the child who will become the third in line to the British throne.
"There are really only two questions: boy or girl? And, what's the name?" Robert Hardman, a reporter with The Daily Mail, tells NPR's Weekend Edition Saturday.
A recent change in the law of royal succession means that for the first time, if Kate and William's first child is a girl, she will keep her place in line for the throne even if a future brother comes along.
Hardman, who spoke to host Scott Simon, says Elizabeth and George are top picks for British punters. If it's a girl, Elizabeth would honor the current monarch, he says. If, on the other hand, the duke and duchess of Cambridge leave St. Mary's Hospital in Paddington with a boy, "George VII would have a nice ring to it," he says.
But if you're hoping to be the first with the news of the royal bundle, don't bother monitoring the palace Twitter feed, Hardman says.
Instead, the tip that the joyous event has occurred will be when a member of the royal household emerges from the hospital clutching a red folder with a piece of paper containing the name, if one's been chosen. Next, they will be driven to Buckingham Palace.
Once there, "the piece of paper will be taken inside, placed in a silver photo frame, on a wooden easel and brought outside the palace and put on display for the world to see," Hardman says.
"There are some things that can still beat Twitter. [Like] an old-fashioned wooden easel," he says.