AN APPARENTLY pathetic mother in Delaware County was charged Friday with the heroin- overdose death of her 11-month-old son.

Christina Rivero, 28, told investigators conflicting stories about the July 15 death of her son, Niccolo Varner, at Mercy Fitzgerald Hospital, Collingdale police said. She was charged with third-degree murder, endangering the welfare of children and other crimes.

An autopsy and subsequent toxicology report found that Niccolo's cause of death was acute heroin intoxication.

Rivero, of Lincoln Avenue near MacDade Boulevard, admitted leaving Niccolo with his older brother, Luciano, 5, in a bathtub, "between his brother [Luciano's] legs," according to the affidavit of probable cause. She went to snort heroin near the garage, the document said.

Authorities don't know how the heroin ended up in the child's system.

Contact Regina Medina at medinar@phillynews.com or 215-854-5985.