Los Angeles -Angelina Jolie, an advocate for adoption, was determined never to get pregnant until Brad Pitt changed her mind, the actress said.

The couple welcomed the birth of their first biological child, daughter Shiloh, in 2006. Twins Vivienne Marcheline and Knox Leon were born in France in July.

'I think one of the life-changing things that he did, one of many, is that I was absolutely never going to get pregnant,' Jolie said of Pitt in an interview in the November issue of W magazine.

'I never felt that it was the right thing to do. Now I wouldn't trade that experience for the world.'

She says she changed her mind while watching Pitt bond with adopted children Maddox and Zahara.

'He stopped talking about having other kids in the other way,' she says. 'So I suppose in my heart I realised he was happy with them as his children, completely. I knew he would never see them as different and that gave me a certain peace.'

After that revelation, 'I suppose I just looked at him and loved him and just felt open to (getting pregnant). I suddenly wanted to. It's one of those things you can't explain,' she says.

She adopted son Maddox and daughter Zahara before having Shiloh. Before the birth of the twins, they adopted a boy, Pax.