Their daughter, whose name has not yet been revealed, was born on Saturday 17 August via caesarean section.
At around eight in the morning, Christina, 33, checked in to the Cedars-Sinai Medical Center in Los Angeles, where other celebrity mums including Kim Kardashian and Jessica Simpson have delivered.
Matt Rutler and Christina Aguilera welcomed their first baby together on Saturday
The Beautiful singer gave birth in her private, deluxe suite where everything went to plan, according to Popdust.
Christina and Matt will no doubt be overjoyed by the arrival of their new addition, who is a sister for Max, the pop star's six-year-old son from her previous marriage to Jordan Bratman.
Film producer Matt popped the question earlier this year with a romantic proposal in Hawaii on Valentine's Day.
The future bride announced the news by tweeting a picture of the couple holding hands against a beachside setting, her finger clearly adorned with her diamond ring. "He asked and I said yes," she captioned the image.
Matt Rutler and Christina Aguilera's baby will be a younger sister to the pop star's son Max
A month later, Christina revealed at a concert that she and Matt were expecting their first baby together.
Home for the happy couple is the Grammy-winning vocalist's new Mulholland Estates mansion in LA, which Christina bought in April 2013 for £6million.
The duo have been together for three years after meeting on the set of her film Burlesque, where he was working as a production assistant. At the time, the songstress was in the middle of her split from her ex-husband Jordan.
Explaining her bond with Matt, Christina has said in the past: "I could depend on him for everything. Matt was working on the movie, and he was so supportive. And he still is. We've been through a lot together."