Matt Damon’s newborn daughter can’t stop smiling when she poops.

The ‘Bourne Ultimatum’ actor, whose wife Luciana gave birth to the couple’s second child Gia last month, revealed his baby is a happy child and enjoys every part of her daily routine.

He said: "She smiles now, mostly when she goes to the bathroom. That's natural."

Matt and Luciana also have a two-year-old daughter, Isabella, and raise Luciana's 10-year-old daughter Alexia from a previous relationship.

The 37-year-old actor admits he worries constantly about his children and his paranoia has even earned him a new nickname.

He said: "They call me 'Red Alert'. If any of the kids were near anything close to being dangerous, I would say, 'Is she touching that?' or 'Watch out!' And the whole family would go, 'Red alert! Red alert!' I guess I can be a bit worried sometimes."

Matt insists his whole life has changed since he became a father.

He said: “There is a lot to love about having kids. The best thing is probably the indescribable way that a new child opens up your heart. It sounds kind of corny but it's true."

Matt and Luciana, 32, have been dating since 2003 and married in 2005.