She had been convicted of intoxication manslaughter and could have faced up to 20 years in prison for the second-degree felony.
Acosta told the jurors that she didn't remember anything about the accident.
Her son, Jesus Navarrette IV, was thrown from the vehicle April 2007 after it skidded on an Odessa street, hit a pole and flipped over. Acosta was holding the baby in her arms while driving and his car seat was in the trunk.
Her two other children also were in the car but were not injured.
Acosta's blood-alcohol level was twice the legal limit of .08 percent.