Kristin Cavallari said on Twitter being a first-time mom is an "incredible feeling."
The reality star gave birth to her son, Camden Jack Cutler, Wednesday.
Cavallari, 25, is engaged to Chicago Bears quarterback Jay Cutler, 29.
The couple announced their engagement and pregnancy in January following a brief split, People magazine reported Saturday.
Cavallari is best known for her work on TV's "The Hills," "Dancing with the Stars" and "Laguna Beach."
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