Ever since the day Nicole Kidman announced she was pregnant, enquiring minds have wanted to know — how did the 41-year-old actress do it?

Far from in vitro speculation, Nicole credits swimming in Australian Outback “fertility waters” during production of her latest film as the reason for her unexpected pregnancy over the past year.

The new mom tells Australian Women’s Weekly in an exclusive interview for the magazine’s 75th anniversary edition: “I never thought that I would get pregnant and give birth to a child, but it happened on this movie. Seven babies were conceived out of this film and only one was a boy. There is something up there in the Kununurra water because we all went swimming in the waterfalls, so we can call it the fertility waters now.”

Nicole also thanks 2-month-old Sunday Rose for her effortless bounce back pre-pregnancy shape. “I’m so lucky I’m so tall, so I carried small and also, I have to say, I had a birth that I was blessed with, a labor that was very good and a baby that was very good to me in that regard. To be given this again is a beautiful thing. To have raised Bella and Connor since I was 25 and now to be able to do it again at 41 … wow!”