Iron Man star Robert Downey Jr debuts as a daddy

Robert Downey Jr and his wife, Susan, have welcomed a baby boy, Exton Elias Downey.

Exton clocked in at 7.24am on Tuesday in Los Angeles, weighing 3.34 kilograms and measuring 50.80 centimetres long, according to various reports.

The Iron Man star had joked with Jay Leno in December that the pregnancy had "been tougher on me" than on his wife. "Just the hormones and the moods stuff and the nausea, and the whole thing."

This was the same interview where he blurted out that they were expecting a boy.

Though this is a first child for the couple, little Exton already has a big brother: Indio Downey, 18, the Sherlock Holmes actor's son from his marriage to Deborah Falconer. The actor married Susan, a producer, in August 2005.