New father Pete Wentz was so stunned to discover his then-girlfriend Ashlee Simpson was expecting the couple's baby, he insisted she send a photo of the positive pregnancy test.

The couple confirmed Simpson was pregnant at the end of May following weeks of speculation, just days after the stars wed.

They welcomed son Bronx Mowgli into the world last month but Wentz admits the baby news initially came as a bit of a shock.

He admits to Details magazine, "(It was) a happy accident."