Chael Sonnen's daughter was born 10 weeks premature last week, Sonnen informed MMA Fighting.

According to doctors, Sonnen's wife, Brittany, contracted listeria, which caused the early birth. The illness has been passed along to their daughter, as well.

The Center for Disease Control describes listeria as "a serious infection usually caused by eating food contaminated with the bacterium Listeria monocytogenes."

In May, the U.S. Food and Drug Administration announced a recall of certain frozen foods manufactured or processed at a Washington facility potentially contaminated by listeria. Several supermarkets were affected by the recall. In July, the CDC declared the outbreak investigation over.

Sonnen is currently unsure how his wife contracted the disease. He has retained the law firm Flesher Schaff & Schroeder Inc. to investigate whether she consumed contaminated food, and they have already reached out to the CDC and FDA on behalf of the Sonnen family.

"She's in a battle and we are prepared to fight," Sonnen said.

Blauna Dian Sonnen was born Friday, Aug. 12, in Portland, Ore. The couple also has an older son, Thero.