SAN ANTONIO (AP) - A San Antonio woman has pleaded guilty just before trial to having a role in the death of her 3-year-old son.

Janie Altamirano's son, Ethan, was found dead in December 2010 with bruises all over his body and a bite mark on his arm. An autopsy found that Ethan died of an abdomen infection that developed after a hard blow.

Jurors and witnesses were ready for trial Wednesday when the 25-year-old Altamirano decided to plead guilty.

She pleaded guilty to serious bodily injury to a child by omission.  Prosecutors say they will seek a 20-year prison sentence for Altamirano.

Her boyfriend at the time of Ethan's death, Michael Pastran, remains charged in Ethan's death.