Kate, formerly Kate Middleton, is currently in hospital being treated for morning sickness. Verifiable facts are thin on the ground, but one thing is known for sure: regardless of the sex of the child, he or she is likely to reign – eventually.
Primogeniture, the rule that male children take precedence in succession to the throne, has been scrapped. The centuries-old tradition was ended last year at a meeting of the Commonwealth of Nations, a supra-national group of countries mostly consisting of former parts of the British Empire.
The laws to do this haven't even been tabled yet, though they may take on a new urgency given the announcement.
Then again, perhaps not that much urgency given it will be a long time before this child basks in the regal glory of coronation anthem, Handel's Zadok the Priest: Queen Elizabeth II shows no signs of quitting the throne at all.
During the 1990s, speculation was rife that she would stand aside to let her eldest son Prince Charles become king. It didn't happen, and is rarely spoken about today.
At this point you may be thinking this is all uncannily like reading tea leaves, and, indeed it is. The monarchy doesn't make much in the way of planning announcements and the speculative stories based on sources "close to" various royals are a stock-in-trade of the British press, particularly, though by no means exclusively, the tabloids.
Getting back to the facts, what we know is that Prince Charles, now 64, is heir apparent to the throne, followed by his eldest son William, aged 30. After him will be the new child and everyone else in line to the throne, such as William's brother Prince Harry (Henry), (currently third-in-line) and uncle, Prince Andrew, (currently fourth-in-line) get bumped one place.
It is unclear whether Queen Elizabeth's second child, Princess Anne, 62, will enjoy a move up due to the end to primogeniture, or languish tenth in line, soon to be eleventh.
The announcement that the Duke and Duchess were expecting was made in a press release and, in a first for royal social media, a rather terse, tweet. (Not a bad day for hierarchy fans on Twitter: the Pope, who is head of state of the world's smallest country, the Vatican City State, joined the social network).
Not everyone is pleased by the news of the royal pregnancy. An online poll undertaken by the republican-leaning Guardian newspaper is currently giving a 64 percent thumbs down to the question: "Do you share David Cameron's delight at news the Duchess of Cambridge is pregnant?" Goodness.
The newspaper also published a snarky comment piece lightning fast.
(This writer's own Facebook feed has cleaved – unsurprisingly, given I'm in Ireland – with about a third excitedly congratulating the couple they will never meet and a further third unreasonably hot under the collar about the potential expansion of the royal line. The final third are, mercifully, silent on the issue.)
On which note, I shall resume my own dignified silence.