Weighing in at 8lbs 6oz, the little one has been named Pearl by her proud parents, according to Hello! magazine.
The couple - who announced their engagement last September after a four-month romance - were expecting their first-born to arrive last Wednesday (20.04.12).
Taking to twitter on Tuesday night (19.04.12), Jack said: "Well @lisamarstelly is supposed to give birth to our baby tomorrow. Fingers crossed."
But by Friday (22.04.12) there was still no progress when Lisa tweeted: "Still pregnant. Apparently I made too lovely of a home int here! #overit #comeonbaby. (sic)"
Jack`s sister Kelly was just as eager to meet her niece, and already has plans for girlie shopping trips.
Sharing her thoughts on the pregnancy, she said: "I don`t have the words to express how excited I am about it. I`m so proud of Jack and Lisa. I couldn`t stop crying when I saw the ultrasound of their baby girl.
"Jack loves his privacy and he`s turned out to be one of the most respectful, well-rounded and honest gentleman around. The two of them are going to make great parents.
"I can`t wait to style my niece. I`ve already told him I`m going to steal her and take her out shopping."