The sports superstar announced in December that he and Hensen were set to become parents.
And Armstrong took to Twitter.com to confirm that his son Max had been born, weighing in at 7lbs.
The Tour De France champ joked on his page, pretending the post was written by the newborn tot: "Wassup, world? My name is Max Armstrong and I just arrived. My Mommy is healthy and so am I!"
Armstrong, who dated rocker Sheryl Crow for three years, has three children with ex-wife Kristin -- Luke and twins Isabelle and Grace.
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