WORCESTER, Mass. — The mother of a missing 5-year-old Fitchburg boy who hasn’t been seen in months and is feared dead pleaded not guilty Friday to additional charges in the case.

Elsa Oliver, 28, was ordered held on $100,000 bail at her Worcester Superior Court arraignment on charges including kidnapping, assault and battery with a dangerous weapon and reckless endangerment. That’s the same bail she’s been detained on since her Fitchburg District Court arraignment in December.

Her son, Jeremiah Oliver, was last seen by relatives in September but wasn’t reported missing until December. The family was being monitored by state social workers at the time.

Oliver indicated at one point Friday that she wanted to represent herself in court proceedings, but the judge talked her out of it after questioning her about her legal training.

Oliver’s next court appearance is scheduled for April 28.