The news of Langdon's baby girl comes after she took a cheeky swipe at co-host Karl Stefanovic on his 44th birthday.
Sharing a photo to Instagram, Karl's fiance Jasmine wrote: "You light up my world...happiest of birthdays my love."
The picture saw the Today host lighting candles on a cake with a home-made flame thrower.
Peter Stefanovic, and Allison's Weekend Today co-anchor, also got in on the birthday action.
"The only time we ever did the weeding," Peter captioned a throwback post.
"Happy birthday to my big brother".
Langdon was quick to comment on the snap with a cheeky quip.
"Such a cute photo. What happened???!!" she wrote.
Congratulations to Allison on her baby news!
For more on Parenting, head to the Practical Parenting site.
