Niccolo Varner spent two months in the hospital suffering withdrawal from his mother’s heroin addiction. The Delaware County Children and Youth agency was notified when the mother, Christina Rivero, had come to the hospital complaining of stomach pain without realizing she was pregnant. The agency later wrote a barebones safety plan to send Niccolo home: The child’s father was not to let Rivero be alone with the baby. “The family began to stabilize,” according to a summary report. The case was closed in May 2012. Two months later, Niccolo died from heroin intoxication. The agency hadn’t realized Rivero was using again. Her public defender, Joseph D’Alonzo, said oversight had “faded away.” Rivero pleaded guilty to involuntary manslaughter and was sentenced to three to six years in prison. Trish Cofiell, county spokeswoman, said caseworkers are being trained in better ways to keep an eye on drug-using parents.