Actress Kaylee DeFer has given birth to her first child with her rocker boyfriend Michael Fitzpatrick.

The Gossip Girl star, 26, became a first-time mother on Friday (20Sep13) when she welcomed a little boy named Theodore Ignatius Fitzpatrick, who weighed in at eight pounds and 13 ounces (3.7 kilograms).

Fitzpatrick was due to perform a show with his band Fitz and The Tantrums in San Diego, California on Friday (20Sep13), but cancelled the gig after DeFer went into labour.

A message posted on the band's page after the birth reads, "Congratulations to our partner in crime Fitz and our beautiful friend Kaylee on the birth of their beautiful son. The world has another superstar!!"