The 33-year-old star and her partner Scott Disick welcomed their second child, a girl they have named Penelope Disick Scotland, at Cedars-Sinai Medical Center on 08.07.12 and she is now "resting" with her family.
Kourtney said in a statement: "Scott and I look forward to welcoming you very much, our little angel Penelope Scotland Disick. We are blessed. Mommy and baby are resting comfortably."
Her mother Kris Jenner has confirmed she had a natural birth and has revealed Penelope has a resemblance to her older brother Mason, two.
She said: "It was a great. She had an easy delivery. Penelope is so cute. She looks just like Mason. She`s so beautiful. We are so happy."
Kim Kardashian also tweeted her joy at having a niece.
She wrote: "Welcome to the world Penelope Scotland Disick!!!! (sic)"
Kourtney and Scott recently revealed they still have therapy to make sure their relationship is strong, but she thinks he has developed as a person since she first met him.
She said: "He`s grown so much over the years. I love seeing him as a dad - he`s great with Mason - and I`m not saying that we`re perfect. We go to therapy, which helps us a lot. I think we`re always working to better ourselves, which I think a lot of people can do.
"I could go into the therapy session despising him, but by the time I leave - even if he`s not in there - I feel like I understand him so much more."