Chen Jing-ni, who was separated from her sister in July, was being taken by a taxi on Monday from a provincial hospital to Shanghai when she died, said a spokeswoman for the Children's Hospital affiliated with Shanghai's Fudan University. Like many Chinese officials, she refused to give her name.
The official said Chen died about halfway to Shanghai from her home in eastern China's Zhejiang province, but that she had few details. Hospital experts were still checking on her cause of death, she said.
Chen reportedly had recovered well from the surgery that separated her from her sister Hu Jingxuan an event that drew considerable media attention in China. Hu died shortly after the surgery.
Both girls had congenital heart problems and shared a liver, spleen, gallbladder and digestive system.
Chen began vomiting and developed diarrhea on Friday. Doctors in Taizhou, her hometown in Zhejiang said the baby failed to respond to treatment for digestive tract bleeding and intestinal obstruction, the official Xinhua News Agency reported.