PITTSBURGH (AP) — A woman poisoned her infant son by repeatedly injecting salt water into his feeding tube at hospitals in Tennessee and Pittsburgh in what she claimed were attempts to hasten the death of a suffering child, authorities said Wednesday.

Four-month-old Noah King is in critical condition with sodium poisoning at Children's Hospital of Pittsburgh, and police said they believe the baby's medical problems were caused entirely by his mother.

Amber Brewington, 21, was charged with attempted homicide and police said she told investigators she had injected her son with salt water five or six times, and that she had severe postpartum depression.