The woman claimed the newborn was her own.
The hospital where a woman brought a baby she had allegedly cut from another woman's womb is now under investigation.
Illinois's Advocate Christ Medical Centre did not immediately report the woman, Clarisa Figueroa, to officials when she arrived to the hospital with the newborn.
The 46-year-old was covered in blood and showed no signs of having been in labour.
NBC News reports that the Illinois Department of Public Health has opened an investigation into the murder of 19-year-old Marlen Ochoa-Lopez.
Ochoa-Lopez was nine months pregnant when she went missing last month. Facebook messages show that she had been in contact with Clarisa arranging to meet.
She had been strangled before her baby was cut from her womb.
Authorities suspect that Clarisa and her daughter Diseree had intended on raising the baby as their own after Clarisa's own son died of natural causes.
The woman had phoned authorities claiming that she had just given birth and that the baby was not breathing.
When she was taken to hospital she was brought to the neonatal intensive care unit. She had shown no signs of being in labour or having given birth.
Police eventually managed to run a DNA test on the baby to confirm that the child, a baby boy, was not Clarisa's.
He belonged to Ochoa-Lopez and has since been reunited with his family. He remains in a critical condition.
Advocate Christ Medical Centre refused to comment on the matter.
They said:
"Our top priority is to provide the safest and highest quality care for the patients and communities we serve.
"Out of respect for patient privacy and in compliance with federal and state regulations, we are unable to provide comment. We continue to cooperate with local authorities."
