Nicole Kidman and Keith Urban expecting their first child

Actress Nicole Kidman is expecting her first child with husband Keith Urban, it has been revealed.

Urban & Kidman, both 40 - have been married for 18 months.

The couple broke the news to their families over the Christmas holiday.

Kidman has already spoken about "winding down" her film-making activities as much as possible next year.

The baby - whose arrival date has not yet been revealed, will be the The Golden Compass star's first biological child; she has two adopted children with ex-husband Tom Cruise – Isabella, 15, and Connor, 12 – but their relationship is strained. "They call me Mom," Cruise's new wife, Katie Holmes, said recently.

Kidman has talked openly about her desire to have another baby. "I'm yearning to have one," she told Vanity Fair in September. "I think I would be very sad if I wasn't able to have a baby. Keith knows I want one, and he has been getting there slowly."

In an interview in February on Oprah Winfrey's Oscar Special, Russell Crowe asked the actress if she planned on getting pregnant. "I hope so," she replied.

Nicole is is due to film The Reader with Ralph Fiennes and British director Stephen Daldry in Berlin next month, but has no more cinema work planned after that.

"I just want to spend as much time as possible with my husband," she told Britain's Daily Mail newspaper.

Earlier this month the actress also dismissed the idea of returning to the stage next year.

"It wouldn't fit in with the logistics and dynamics of my family", she said - a remark given extra meaning by the news of her pregnancy.

Her most recently-released film is the extravagant fantasy The Golden Compass.

Although the film was attacked by some critics, the actress's performance as the glamorous villain Mrs Coulter won wide praise.