The body was found Friday in a Wilkinsburg apartment of another woman who showed up at a hospital with a newborn she falsely claimed was hers.
The body "was in a state of moderate decomposition" and appeared to have been dead for about two days before it was found, Allegheny County Medical Examiner Karl Williams said in a statement Saturday.
The woman's hands and feet were bound with duct tape, and her face was covered with a plastic material that had also been secured with duct tape. A placenta was recovered at the apartment.
Investigators were trying to determine the woman's identity, how she died and whether she was the mother of the baby that Andrea Curry-Demus, 38, of Wilkinsburg, allegedly told police she obtained for $1,000.
Curry-Demus showed up at West Penn Hospital in Pittsburgh on Thursday with a newborn that still had its umbilical cord attached, police said. Tests later proved she was not the mother - despite her claims to the contrary, police said.
Curry-Demus was charged with child endangerment and dealing in infant children. She has been jailed until she posts $10,000 bond and undergoes a psychiatric exam.
It wasn't clear if she had an attorney.
The woman's body was found Friday after reporters called authorities about a foul odor coming from inside Curry-Demus' apartment. Police had been at the building Thursday night, but did not go into that apartment, Wilkinsburg Police Chief Ophelia Coleman said. Instead, a relative of Curry-Demus led them to another apartment, she said.