Amid the frenzy caused by Clarence House on Monday morning when it announced the pregnancy, people immediately rushed to link the news with the Scottish independence referendum.
Sky News, tracking Alistair Darling on the campaign trail, asked the leader of the pro-union Better Together campaign how it would "play" in the referendum.
But Darling refused to be drawn on the matter.
"Everybody would offer the Duke and Duchess the warmest congratulations and the vey best," he said. "But I am quite sure all that all of that is completely above politics."
Pressed again on whether the news would help sell the idea of Britain to Scottish voters, Darling replied: "I always believe we are better together."
However Alex Salmond could not resist a sly joke. "Congratulations & best wishes to the Earl & Countess of Strathearn. Wonderful to hear they're expecting their second baby – very happy news!" he tweeted, using the couple's Scottish titles.
Congratulations & best wishes to the Earl & Countess of Strathearn. Wonderful to hear they're expecting their second baby – very happy news!— Alex Salmond (@AlexSalmond) September 8, 2014
David Cameron, who spent the weekend with the Queen at Balmoral, will attempt to convince sceptics this week that Scotland will get significantly more autonomy even if independence is rejected.
The move comes amid reports that the Queen is "horrified" at the possibility of Scotland leaving the United Kingdom. A Buckingham Palace spokesperson said the Queen is “strictly neutral” in the independence debate but admitted she is taking a “close interest” in the vote.
Darling has insisted he is "very confident" that voters will reject independence, despite a shock poll suggesting the United Kingdom could be consigned to history when Scots vote on 18 September.
He said the gap between support for the Yes and No campaigns had always been expected to narrow and dismissed claims that the pro-union campaign was now being forced into panic measures to shore up support.
But the snowballing momentum behind the separatists has sent the pound plummeting to a 10-month low of just below 1.62 versus the US dollar and Scotland-based financial institutions have also taken a hit, with Royal Bank of Scotland, Lloyds Banking Group and Standard Life shares falling by more than 2%.