Holly Willoughby was forced to miss This Morning on Monday after her youngest son Chester suffered a "nasty cut" to his head in a fall.
Co-host Phillip Schofield revealed what had happened to viewers who noticed Ruth Langsford sitting in Holly's normal spot.
Phil was quick to reassure viewers that one-year-old Chester was fine as he explained her absence.
He said: "Ruth's standing in today because - before I go any further with this story, he is alright - Chester, her youngest son, yesterday afternoon fell over and banged his head. He's got a very, very nasty cut on his head.
"They dressed it overnight and today he has to go back into hospital to get stitches so that's where Holly is.
"He is absolutely fine, he was playing afterwards but it is a really nasty cut."
Holly posted a photo on Instagram confirming that Chester was OK.
Thanking Ruth and the show, she wrote: "Thank you for all the lovely kind messages... Chester is just fine and was definitely the bravest out of all of us...
"He received brilliant care from everyone at the #Chelseaandwestminster hospital, makes you realise again how lucky we are to have such a wonderful #nhs."
Holly, 35, has two other children with husband Dan Baldwin: son Harry, 6, and daughter Belle, 5.
She missed out on the excitement of Phil being reunited live on the show with his favourite identical twins, Australians Anna and Lucy DeCinque.
He had previously spoken to them with Holly as they opened up about sharing a boyfriend. This time they appeared on the show as a surprise, with Ruth whipping off a sheet covering a car to reveal them inside.
Buttering Phil up by calling him "TV royalty", the two talked about their experience in London with their boyfriend and how their identical lives had impacted their sightseeing in the capital.
Speaking over each other, they said: "We need to do the same steps to burn the same calories.
"If she puts her knife and fork down, I put my knife and fork down.
"If she sips from a glass of water, I sip from a glass of water."
The duo said they hope to get pregnant by their boyfriend at the same time, but revealed one difference, stating that Anna has a scar on her face while Lucy has a mole.
Ruth said she was "mesmerised" by the twins.