A sexual assault investigation has been launched after a woman in a vegetative state for several years gave birth, according to US reports.
The woman is a patient in a clinic run by Hacienda HealthCare near Phoenix, Arizona.
The clinic said it was aware of a "deeply disturbing incident".
Local reports say the healthcare centre is conducting an internal investigation and co-operating with Arizona police.
A Phoenix police spokesman said "the matter is currently under investigation".
Staff were unaware the woman, believed to be 20, was pregnant until the baby was born, according to Fox 10 news.
CBS Phoenix affiliate KPHO-TV reported the woman gave birth on 29 December to a health baby.
The Arizona department of health services said it had sent inspectors to the facility, checked on the patients treated there and had implemented "heightened safety measures" following the birth.
A spokesperson for the department said: "Upon learning of the allegation, Arizona Department of Health Services (ADHS) immediately initiated an onsite complaint investigation to ensure the health and safety of the patients and ensure the facility is in compliance with all state laws and regulations.
"During this time, the agency has required heightened safety measures be implemented at the facility including increased staff presence during patient interactions, increased monitoring of the patient care areas, and increased security measures with respect to visitors at the facility."
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Hacienda Healthcare spokesman David Leibowitz said the group was "fully committed to getting to the truth of what, for us, represents an unprecedented matter".
A second spokesperson for the facility said: "We cannot comment on any ongoing investigations. We can say that our patients' and clients' health and safety is our number one priority and that we always cooperate, when asked by any agency, in an open and transparent way."