The girl, Simpson's second child (her first was son Bronx, with ex-husband slash Fall Out Boy bassist Pete Wentz; Bronx is now 6 years old), was born Thursday night, July 30.
In April, Simpson told People that though she's not a first-time mom, she had plenty of learning to do still.
"I think that no matter what, with every child it’s different. It feels new to me too, and it’s been six years, so I’m like, ‘Here we go! We gotta learn how to get the swaddle on again!'" she said.
Pics of Simpson's wedding to Ross, which they made official nearly a year ago, were recently published. Let's just say that the pop songstress and Ross, son of musical legend Diana Ross, look like a match made in musical heaven.
Congratulations to the happy couple!