The 'Pieces of Me' hitmaker and the 'Hunger Games' actor confirmed the birth of their little girl on their Instagram accounts.
They both posted an identical image, which read: ''We are overjoyed about the birth of our precious baby girl, Jagger Snow Ross.''
And the pair couldn't be happier with their new arrival.
A source told PEOPLE magazine: ''Ashlee is doing amazing and their daughter is perfect. She's gorgeous!''
And the couple had the little one's name chosen for a while.
About the moniker they had chosen, Evan said previously: ''It's unique. You guys will figure out the story behind it once we tell the name.''
The pair have made no secret of the fact they were looking forward to welcoming their little girl.
Evan wrote on Instagram recently: ''#reflections of such a beautiful wedding. Me and my amazing wife @ashleesimpsonross. At my mothers house in Greenwich Connecticut! And now I can't wait to meet my little baby girl. (sic)''
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