She captioned the post: “Georgia May and my grandson Dean Lee Jagger Sedlick.”
The new parents have been flooded with good wishes and congratulatory messages from Georgia’s famous pals and fans.
Sir Mick’s ex-wife Bianca commented: “Dear Jerry congratulations grandma. Dean is a lovely boy like his mother, @georgiamayjagger and his grandma xx”
Model Immy Waterhouse replied: “Awhh!!! Congratulations.”
Georgia revealed she was pregnant back in June, alongside a series of snaps of her growing baby bump.
She wrote on Instagram: “Patiently waiting for our new best friend @cambryans.”
She previously revealed the advice her mother had passed on to her.
She told Harper’s Bazaar last year: “I am trying to get better at doing the things that scare me – I have always been terrified of public speaking, I’ve had huge anxiety around it but I had this opportunity to give out an award at the BRITs this year and I thought, ‘I am just going to do it’.
“My mum always says ‘Make hay while the sun shines’ – I don’t want to feel regret about saying no to great opportunities just because I feel nervous. And there is nothing better than that feeling afterwards when you do something you are afraid of.”