Kate, 36, is expecting her third child and she's been told it will come on or around the feast day of the patron saint of England.
It's understood the mum-of-two doesn't know if she's having a girl or a boy – preferring a surprise - but has been told to expect it around 23rd April.
And, like the births of Prince George in 2013 and Princess Charlotte in 2015, she'll have the baby at the private Lindo Wing of St Mary's Hospital in London.
A royal source said: “There's no certainty with due dates of course but the Duchessis working off a date around St George's Day and it would be a lovely patriotic coincidence if he or she were born then.
“The one thing that is certain though, if it's a boy he wo't be called George! Prince George has already taken that one.
“Or if she's very late, as she was with George's birth, she could even make it a very special wedding anniversary present to William, as they celebrate seven years of marriage on the 29th April.” Kate looked swell this week as she wore blue two days in a row (Tuesday & Wednesday) – leading bookies to say it was evens she was having a boy.
But a late April baby does not give Kate much time to get over the birth in time for Harry and Meghan's wedding three weeks later.
A spokesman for the couple declined to comment.