Before revision: The Care and Feeding of Children: A Catechism for the Use of Mothers and Children's Nurses (1907 edition) by Dr. Holt, L. Emmett, MD CIO is any sleep-training method which allows a baby to cry for a specified period before the parent will offer comfort.
After revision: CIO is any sleep-training method which allows a baby to cry for a specified period before the parent will offer comfort.