Stacey Joy Bourdeaux, 34, pleaded guilty in Court of Queen's Bench to manslaughter in the death of her son Sean Fewer in 2004.
Bourdeaux also pleaded guilty to failing to provide the necessities of life and attempted murder of her older son last May.
When Bourdeaux's 10-month-old son was found in his crib not breathing in December 2004, it was believed he had died of natural causes.
But that was reassessed after Bourdeaux brought her five-year-old son to Alberta Children's Hospital in 2010.
He was shaking, incontinent and unable to stand, symptoms police said were consistent with some form of trauma.