Kidman already has two children, but both were adopted
Nicole Kidman has credited a waterfall with bringing about a flurry of pregnancies - including her own - on the set of one of her films, Australia.
The actress said seven babies had been conceived during production of the film in a small town in Australia's outback.
"There is something up there in the Kununurra water", in which she and six other woman swam, she told The Australian Women's Weekly.
Kidman, 41, gave birth to her daughter, Sunday Rose, in July.
She is married to country music singer Keith Urban and has two children - both adopted - from her previous relationship with fellow star Tom Cruise.
Kidman filmed Australia, directed by Baz Luhrmann, in Kununurra, a small town in the far north of the state of Western Australia.
"I never thought that I would get pregnant and give birth to a child, but it happened on this movie," she said in the interview.
"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."