It's a Fall Out Boy for Ashlee & Pete!

(WireImage)

Congratulations to Ashlee Simpson and Pete Wentz!

The flame-haired singer gave birth to a bouncing baby boy on Thursday, Nov. 20, at Cedars-Sinai Medical Center in L.A. The baby, named Bronx Mowgli Wentz, weighed in at 7 lbs., 11 oz. and measured 20.5" from head to toe.

A statement from the younger Simpson sister's rep to OK! reads, "Ashlee, Pete and baby Bronx are all healthy and happy, and thank everyone for their well wishes!"

Ashlee checked in to Cedars-Sinai around 5am on Thursday morning and was placed on the 3rd floor maternity ward — in the same suite that Julia Roberts used when she had her twins!

This is the first child for Simpson, 24, and rock star hubby Pete, 29. Although OK! broke the news that Ashlee was pregnant back in April, the couple formally announced they were expecting in May, after weeks of speculation and photos showing the pop star's growing baby bump.

"While many have speculated about this, we wanted to wait until after the first trimester to officially confirm that we are expecting our first child," announced Pete and new bride Ashlee, using her new last name for the first time, on the Fall Out Boy bassist's web site, FriendsOrEnemies.com. "This is truly the most joyous time in our lives and we are excited to share the happy news and start our family."

Perhaps they just wanted to make it official first.

Just before announcing her pregnancy, Ashlee wed Pete in a lavish and top-secret ceremony at the Simpson pad. Bridesmaids included Ash's sister, Jessica Simpson.