The presenter, who gave birth to her third child Chester a year ago, has reflected on how quickly time has passed.
On the morning of Chester's birthday, she tweeted: "Happy 1st birthday to our gorgeously perfect wonderfully beautiful Chester... Where did that year go?"
Willoughby, 34, has two other children - Harry, six, and Belle, four, - with husband Dan Baldwin.
Willoughby, who rarely shares photos of her children, uploaded an adorable photo holding Chester's hand, which was neatly laid on her palm.
Within minutes she had received thousands of happy birthday messages for her son from her 6.13 million fans on Twitter.
They too, seemed to comment on how quickly the year has gone since she gave birth.
Willoughby announced recently in an interview that she doesn't want any more children.
Speaking to The Sun, she said: "We keep having babies. But I am done now. I am not going anywhere."