Amanda Jo Stott-Smith was indicted on eight counts of aggravated murder and attempted aggravated murder Tuesday. She is being held in Multnomah County Jail.
Her 4-year-old son, Eldon Smith, died May 23 after falling into the Willamette River in Portland. His 7-year-old sister was rescued by residents who heard her moans in the darkness and jumped into their boat to investigate.
Police have not said how they believe the children fell from the bridge.
Court records show Stott-Smith and her husband, Jason Smith, fought for custody of their children after he left their Tualatin home last year and moved to Eugene. With the couple's divorce case pending, a judge in April granted Jason Smith custody of the children.
Stott-Smith had parental visitation rights.
The girl made a miraculous recovery after surviving the fall and 30 minutes in the river. She was hospitalized for several days and is now in Eugene with her father.
The state Department of Human Services has said it will conduct an internal review of its dealings with Stott-Smith.
She is scheduled for a court appearance Wednesday.