Thurlow announced the new arrival with a post on Instagram, sharing a series of pictures of their daughter Nell Sophia.
The couple, who met during the 2017 series of Love Island, were congratulated by their former co-stars.
Chris Hughes said: “Just fantastic. Congratulations.”
Amber Davies commented: “OMG congratulations. absolutely wonderful news Cam! Xxxx”
And Gabby Allen wrote: “omg congrats beautiful.”
Dr Alex George, who appeared on the 2018 series of Love Island, said: “So pleased for you.”
And Olivia Bowen, who finished second on Love Island 2016, said: “Congratulations both of you she is absolutely adorable.”
Announcing the birth, Thurlow said: “Nell Sophia Jewitt 4:32am 27th October 6lb 5oz.
“There may be a thousand new photos on my camera roll, but none of them could ever do justice to the way you have lit up our lives.”
Thurlow and Jewitt announced they were expecting a baby together in May, nearly three years after meeting on the show.
On Sunday she revealed the baby was overdue and wrote on Instagram: “I do have a habit of overcooking things and it looks like this little bun is no different!
“Happy to have an extra few days to relax now though, after spending some quiet time offline getting organised.
“Now it’s just about relaxing, keeping up with the laundry and restocking the snack cupboard each time @jamiejewitt_ eats all the hospital bag snacks (and then secretly restocking it again when I eat them all).”
