But how do we know when nothing has been announced?
The biggest giveaway about Kate's current state for royal watchers is not a telltale bump... but rather the Duchess of Cambridge's hair!
Royal fans have pointed out that, at the start of her previous three pregnancies, Kate has changed - and she was showing off a new shorter 'do when she took Princess Charlotte for her first day of school earlier this month.
One royal watcher tweeted: “Kate just changed her hair, which she always does to distract us when she’s newly pregnant."
And it wasn't just one royal fan who noticed Kate's new style:
"New hair cut is Kate pregnant again??" asked another, while a third commented, “She always sports a new hairstyle when she’s pregnant.”
Nine months before George's birth in 2013, the Duchess had a darker 'do, then prior to her pregnancy with Charlotte in 2014, Kate gave a fringe a try. Ahead of announcing she was expecting little Prince Louis in 2017, the Duchess had her hair did again... so this evidence is pretty strong!
“We’ve suspended betting on Kate, who is most likely to give birth in 2020," Ladbrokes' Alex explains.
"Elsewhere, 8/11 says Meghan gives birth to a second baby in as many years, with the Duke and Duchess of Sussex making it no secret they’re keen to add to their family.
“Meghan was 2/1 to have another baby by end of 2020 last month, but a flurry of bets around the country has forced us to cut odds to 8/11 now, with punters convinced an announcement for a second baby will come sooner.
Meanwhile, speculation about a possible second pregnancy for Meghan, Duchess of Sussex, hit fever pitch after the actress-turned-royal wore not one but two of her early pregnancy dresses while on tour in Africa recently.
On the first day of the tour, Meghan made a nod to her first child Archie by wearing the same vibrant blue frock she wore during her pregnancy.
According to Express, the photos created a buzz online amongst royal observers, with one user writing "Meghan Markle changes into the same blue dress she wore when she was pregnant last year on Royal Tour!”
In a following royal engagement, Meghan donned a striped maxi dress that she'd also worn soon after revealing she was pregnant with Archie.
Royal expert Katie Nicholl told ET. "This dress was significant because she stepped out in it just days after announcing her pregnancy, which I think has led to some speculation that 'Could we be hearing imminent news of another royal baby?'"
Finally, Princess Eugenie - who married her beau Jack almost a year ago - has also set rumours swirling that a pregnancy announcement is imminent. The pair had planned to have children “as soon as they can”, royals biographer Ingrid Seward told People magazine.
And Ladbrokes' Alex confirms that baby news will be breaking soon for the daughter of Fergie, Duchess of York.
“Eugenie is as short as 1/2 for a 2020 baby," he says. "Couple that with the fact we’ve suspended betting on Beatrice tying the knot, we’re anticipating next year to be the busiest ever on a royal betting front.”