"It is with great sadness that we inform you of the passing of baby Yovanny Jadiel Lopez", the statement said.
The baby was on life support but his condition rapidly deteriorated.
"He suffered irrevocable brain damage", Ms Contreras said, according to local TV station WLS. "There's no medicine, there's no pill that can fix that".
Yovanny initially survived after his mother, 19-year-old Marlen Ochoa-Lopez, was attacked in May after being lured to a woman's home in Chicago, responding to a Facebook offer for free baby clothing. She was then strangled and her unborn baby cut from her.
Ochoa-Lopez, 19, was discovered dead on May 15, three weeks after she'd gone missing just ahead of her due date.
As the baby was fighting for his life, a picture emerged of him with his father.
Doctors wouldn't speculate on the baby's survival chances, but there was hope after he opened his eyes at the end of May.
"We were just praying and praying and he opened his eyes, and his dad said, "Oh my God, he opened his eyes!'" Cecilia Garcia, a student pastor who is assisting the family, told CNN".
A mother and daughter are charged in Ochoa-Lopez's killing.
Prosecutors said Clarisa Figueroa, 46, claimed she had given birth to the baby when she took him to a hospital on April 23. Clarisa Figueroa's partner, Piotr Bobak, 40, was charged with concealment of a homicide.
All three are set to be arraigned June 26, court documents show.
A baby has died after he was cut out of the body of a Chicago teenager weeks earlier, WGN reports.
The suspects allegedly planned the attack for months.
She and her 24-year-old daughter are charged with first-degree murder. In October, she announced she was pregnant, which surprised her family because her fallopian tubes were tied.
They said she plotted for months to acquire a newborn, and that she posted an ultrasound and photos of a room decorated for a baby on her Facebook page. She didn't know whether Yovani Lopez, Ochoa-Lopez's husband, was with his son at the time of death, though she noted he regularly spent the night at the hospital. Figueroa offered her clothes for the baby and suggested they talk in a private message.