The Jan. 20 incident initially wasn't reported to law enforcement. The Richmond County School Safety Department stepped in to investigate only after Lt. Richard Roundtree got a call from a Chronicle reporter.
School officials have thus far refused to comment on the baby's condition, saying only that the teacher was examined by a school nurse, instructed to see her physician and on leave for three school days after the incident.
The teen, a special needs student, is charged with aggravated battery in the attack, during which a teacher -- trying to break up a fight -- was struck repeatedly on her body and "intentionally" in the stomach, according to a complaint Roundtree submitted to juvenile authorities.
A petition filed Thursday by the state Department of Juvenile Justice says the boy committed aggravated battery against the teacher by "rendering a member of her body, to wit: an unborn fetus, useless by punching said victim in the abdomen." Roundtree's report says she was approximately 10 weeks pregnant at the time.
Reports obtained from the school system by The Chronicle say the attack happened as the 13-year-old brought his 12-year-old brother, also a special needs student, to the teacher's class to confront another student who "had been bothering him."
According to one report, the 13-year-old left his class to get his brother, and when they entered the pregnant teacher's room she asked them to leave, "but they refused."
As the two brothers approached the student, the teacher stepped between them "and immediately began being struck in the stomach and arms by (the 13-year-old) offender."
A tribunal report says the older brother "hit a teacher in the eye, knocked over a podium onto a student, causing injury to the student, and hit a pregnant teacher on her arm and in her stomach."
The teacher finally pushed the brothers out of the class and they were taken to the school office.
Initially, the school system's safety office wasn't notified by the school's principal, Thomas Norris, who said he reported the case to the school system's central office.
After learning about the incident five days later, Roundtree initiated an investigation to determine whether criminal charges were warranted.
He said at the time that his office prefers to be called in immediately anytime a teacher or student is injured.
Neither Norris nor Roundtree returned calls Thursday. Superintendent Dana Bedden was in Texas, where he is a candidate to head the Irving Independent School District.
After a Feb. 2 tribunal, the 13-year-old was assigned to Tubman Education Center Alternative Program for two years, but the panel agreed to revise that decision should the student become eligible for the Georgia Network for Educational and Therapeutic Support program.
His younger brother, who officials said did not strike the teacher, was suspended for five days.
After the teen was charged criminally on Feb. 5, he went to juvenile court for a detention hearing. Judge Ben Allen said he appeared heavily medicated, so he ordered him to be sent to Serenity Behavioral Health to have his medications adjusted.
The judge also ordered that he wear a tracking ankle bracelet and undergo a psychological competency evaluation.
"We need to know something about him, mentally," Judge Allen said.
An arraignment date hasn't been set.
Staff Writer Preston Sparks contributed to this article.