Nicole Kidman and Hugh Jackman grappled with life-changing events on-screen and on-set in their sweeping new romantic adventure 'Australia.' What secret did Nicole think she could keep for the duration of the shoot?

Asking questions of each other via the Flip Video Mino Camcorder, Hugh kids Nicole, "Did you really think that you kept it a secret from everybody that you were pregnant on the shooting of the film?"

Nicole responds, "I thought I did. Subsequently I found out that I was a hopeless secret keeper -- that's more that my belly wasn't such a good secret keeper, and also because I had morning sickness and I was tired; you know, the first three months when you're pregnant you're tired." Of course, Nicole and hubby Keith Urban gave birth to daughter Sunday Rose in July.

In theaters everywhere Wednesday, 'Australia' places Nicole and Hugh in an epic saga set in the days leading to World War II. Nicole plays Lady Sarah Ashley, and English aristocrat who reluctantly teams up with Hugh's Drover, a rough-and-tumble local who guides her to the land she inherited.

As they bicker and bond across their long, rugged journey, the Japanese bomb the city of Darwin and they find themselves dragged into the deadly undertow of World War II.

Shooting conditions in the rugged Outback was not easy, including incredible heat, and Hugh reveals, "Both Nic and I fainted; I fainted on the first day, which I think set the tone for the movie." He adds, "There were dust storms, we had floods, and yet we loved every minute of it."

Watch ET for more with Nicole and Hugh!