Until now, Kate and Prince William have kept the public guessing, but during a visit to a children's centre in Woolwich, east London, the Duchess spilled the beans. Christine Osborne, a 49-year-old volunteer, asked when her baby would be born, and received the reply: "I'm due mid-April, to the end of April. Not long to go now."
It means that if the Duchess's second child is just a few days late, it could be born on or around the day of the general election on May 7.
Christine, a grandmother who has worked for the Home-Start family support charity for seven years, said: "I couldn't resist asking.
"It's very exciting – and it was wonderful to have her here."
Babies were very much the order of the day during the Duchess's visit to the Brookhill Children's Centre.
She was introduced to families who had been helped by the charity, including Charlene Roper, 25, and her partner Graham Wilders Jnr, 32, who were with their three-month-old daughter Francesca, the youngest of their three children.
Charlene explained how she had sought the help of the Brookhill Children's Centre and Home-Start when her eldest child, now three, was born.
She said: "I just wanted to learn how to do things better so that I could give me children the best possible start in life."
The Duchess also commiserated with some of the mothers at the coffee morning about sleeping patterns and feeding routines.
"It can be hard, can't it," she said sympathetically.
She also spoke with a group of mothers, who did not wish to be identified, who had suffered with post natal depression.
Head of communications Annie O'Brian explained: "The Duchess made clear in advance of the visit that she was keen to speak to them as post-natal depression can have such a knock-on effect on every aspect of family life."
More on Parentdish: