JULIA PLAYS BIRTHING COACH

Oh-so-pregnant America's Sweetheart JULIA ROBERTS was enjoying a chat about motherhood with an about-to-be first-time mom working as an extra on her new flick "Fireflies in the Garden" - and the woman's water suddenly broke!

Freaking out, she screamed that she wasn't even due yet, but Julia quickly calmed her - then started talking her through the contractions that had already started.

As medics lifted the woman onto a cot, Julia comforted her and promised: "The baby will be fine!"

When an ambulance arrived and whisked the woman to a hospital, Julia personally phoned the husband to alert him.

Next day, the star whooped for joy when she heard wonderful news from the hospital - mother and baby girl were doing just fine.