Keith Urban's Surprise Birthday Sing-ALong

During a Saturday concert in Chicago's famous Soldier Field, country star Keith Urban gave his pregnant wife, Nicole Kidman, a big crowd-tastic surprise.

According to People.com, after singing "Who Wouldn't Wanna Be Me," he told the crowd that it was Kidman's birthday Friday.

Just before he brings out the glowing actress, he said, "So it would be nice to have 50,000 people sing 'Happy Birthday' to her."

The actress turned 41 on Friday. After the loud sing-along from the whole stadium, she blew a kiss to the crowd and returned backstage.

The couple's first child is due any day.