The 47-year-old actress welcomed daughter Sunday Rose in July 2008 and daughter Faith Margaret in December 2010 with rocker husband Keith Urban.
Kidman is also the mother to two adopted children from her previous marriage to Tom Cruise, reported Us magazine.
"I had my last one at 43. My grandmother had her last at 49. Every month, I'm like, 'I hope I'm pregnant!'... I wish I was!," she said.
The actress revealed that she decided to marry Urban after dating him less than a month because she wanted to know him gradually.
