Poston was providing day care services out of her home for the infant, the 6-month-old daughter of a Jackson couple.
On March 28, the child began experiencing difficulty breathing and went into a seizure while in Poston's care, the sworn statement said.
The child was transported to Saint Francis Medical Center, where she was diagnosed with hemorrhaging of the brain and retinal hemorrhaging in both eyes.
The injuries were consistent with abusive head trauma, the physician who examined the child told authorities.
The infant was airlifted to a St. Louis hospital and multiple tests were performed, revealing several previous injuries consistent with the time the child began staying at Poston's, investigators learned after interviews with parents.
About a month and half before the injury, the child's mother told police she remembered getting home from day care and finding her daughter's mouth bleeding. Poston denied knowing how it had happened, but said there was blood on the baby's blanket.
"This was a violently-inflicted injury, consistent with shaking or other intentional application of force," the statement said.
Poston is held on $10,000 bond.