It's a boy for Ashlee and Pete

Bronx Mowgli Wentz weighed in at 7 pounds 11 ounces, and 20 and a half inches long.

"Ashlee, Pete and Baby Bronx are all healthy and happy, and thank everyone for their well wishes!" a spokesperson for the pair said.

It has been reported that the pop star pair named their child 'Mowgli' after the famous character from the Rudyard Kipling classic, 'The Jungle Book'.

Simpson, 24, was spotted leaving her home Thursday morning and heading straight to Cedars-Sinai Medical Center in Los Angeles.

It was reported that Ashlee arrived at the hospital shortly after 8am, and doctors induced her labour.

Fall Out Boy guitarist Wentz and her big sister Jessica were believed to be at the hospital to support Ashlee.

While her assistant and her father Joe reportedly showed up at the West Hollywood medical center later in the afternoon.

Mystery surrounded the birth of Ashlee and Pete's first born earlier in the week when it was reported that Simpson was taken to Cedars-Sinai last weekend.

However, the pair, who are keen bloggers on their personal websites, remained silent about the pregnancy.

In a taped interview on The Ellen DeGeneres Show on Monday, Jessica Simpson nearly put her foot in it by revealing if her sister's baby is a boy or girl.

When the show's host asked Simpson the sex of Ashlee's baby, Simpson paused before saying: "I can't say because they haven't said. They know, but I don't want to stick my foot in my mouth and get in trouble. I wouldn't be a good aunt."