Cate Blanchett's children have taught her about ''compromise.''

The 45-year-old actress believes she's learnt more about life since becoming a mother to Dashiell, 13, Roman, 10, Ignatius, six, and little adopted newborn Edith because they've forced her to come face-to-face with ''failure'' over the years.

Speaking in the April issue of Vogue Australia, she said: ''Children teach one about compromise. Before having children the idea of compromise rubbed shoulders with weakness or deception.

''They are spirited, passionate, political and demanding. They constantly extend parents and so parents are constantly confronted with their failures.''

The 'Blue Jasmine' star added a little girl to her brood with her husband Andrew Upton after adopting her from the US earlier this month and is over the moon with the tiny tot.

She said last week: ''There's a lot of children out there that don't have the good fortune of our biological children so it's lovely to welcome a little girl. We're besotted.''

The couple - who have been married since 1997 - are planning to relocate to the US once Andrew's term as artistic director at the Sydney Theatre Company wraps up at the end of the year.

Andrew, 49, explained: ''We're all looking forward to spending more time together in one place. We spent nine years living in England and we loved it. But now we'd like to try America.

''They have terrific [opportunities in] television there and Cate has a very strong film career there, too, obviously.''

Cate first sparked rumours she had become a mother for the fourth time after she was spotted holding the newborn on-board a flight from LAX to Sydney on March 7.