Officials at Deaconess Medical Center, citing privacy laws, refused to release additional information.
Police in Kennewick provided no new details on the of the child's mother last weekend. A woman has been jailed for the attack and the investigation is continuing, police spokesman Mike Blatman said.
Police cannot say if the two women knew each other and were trying to determine the motive for the attack, Blatman said.
Araceli Camacho Gomez, 27, of Pasco, was found dead of multiple stab wounds in a Kennewick park. She had been attacked late Friday night, her hands and feet were bound with yarn and an autopsy showed she died of chest wounds.
"The autopsy indicated additional cuts in the area of the uterus consistent with the cutting of the body to remove the child," Blatman said.
Phiengchai Sisouvanh Synhavong, 23, of Kennewick, remained in the Benton County jail without bail after being arrested for investigation of aggravated first-degree murder. She tried to pass the infant boy off as her own in calls made late Friday night to emergency dispatchers, police said.
Arraignment is scheduled Wednesday in Kennewick. If Synhavong is charged with aggravated murder, Prosecutor Andrew K. Miller will then have 30 days to decide whether to seek the death penalty.
There is no telephone listing for the name Synhavong in the Tri-Cities area, which includes Kennewick, Pasco and Richland, but family members told KEPR Television she had been telling them she was pregnant and acting strangely in recent days. They said she worked with senior citizens and knew Camacho Gomez from work.
Friends of the dead woman's family told the Tri-City Herald that a woman, believed to be Synhavong, met Camacho Gomez on a bus Friday and offered to give her some baby clothes.
Synhavong, a 2004 graduate of Southridge High School, was married in May to Keun Synhavong, 35.
Five of her relatives attended a court hearing Monday in which Phiengchai spoke only to pronounce her name and to confirm that she understood her rights. A lawyer, Christopher A. Swaby, was appointed to represent her.
According to documents filed in court, blue mechanic's gloves soaked in blood, a boxcutter, bloody paper towels, yarn, a mucus bulb, baby bottle and baby socks were found in her purse. The court filings did not indicate whether the boxcutter was used to cut or stab Gomez.
Court documents allege that Synhavong called 911 at 11:04 p.m. Friday saying she was at a store, had just given birth and that she thought the baby had died.
The call ended, but the woman called again a few minutes later. Dispatchers traced the calls, and she was found in a parking lot with the baby, holding what appeared to be an umbilical cord. A "significant amount of blood and pieces of human tissue" were found in the back seat of a vehicle, documents said.
The site was a mile or two from the spot where Gomez's body was later found in Columbia Park.
Synhavong and the baby were taken to Kennewick General Hospital, where medical tests showed she had not recently given birth.
Camacho Gomez was found dead around 1 a.m. Saturday.