(Cover) - EN Showbiz - Nicole Kidman has spoken about the roller coaster ride with fertility she has been through.

The actress has two-year-old daughter Sunday Rose with her husband Keith Urban, and they welcomed another girl called Faith Margaret in December. The tot was born via a surrogate, and Nicole and Keith kept the pregnancy a secret until after her birth.

The 43-year-old also has adopted kids Isabella and Connor with her ex-husband Tom Cruise, and previously admitted having children has been a struggle for her. She has suffered an ectopic pregnancy and miscarriage, and has now discussed her decision to use a surrogate.

Ive had a roller-coaster ride with fertility. Anyone thats been in the place of wanting a child knows the disappointment, the pain and the loss you go through. Struggling with fertility is such a big thing and its not something that I would run away from talking about, she told Australias 60 Minutes.

Shes the most wonderful woman to do this for us. We were desperately wanting another child and I couldnt get pregnant. I get emotional talking about it because Im so grateful.

Nicole and Keith are now settled in Nashville, and Nicole is enjoying being there with her family. Motherhood is the most important thing in her life, and the star is constantly amazed by how deep her love is for her kids.

Children are children you'll die for your children," she explained. "And when you feel that as parent that's the unconditional love.

During the programme Nicole showed off photographs of her kids, including one where Sunday Rose is cuddling Faith Margaret. She loves the shot, and discussed which of their parents the two girls take after.

"She's [Faith] got red hair. Sunday had red hair and then it went blonde. Sunday is very much her dad. Everyone says Faith is more me, she said. (C) Cover Media