The 12-week-old sisters were born connected at the hip and lower spine, and shared one lower bowel, the Xinhua news agency reports . On Tuesday, they underwent five hours of surgery at Fudan University Children's Hospital in Shanghai, a centre which specialises in separating conjoined twins. To prepare for the operation, doctors at the hospital sent data gathered from CT and MRI scans to a 3D printing company, which then built two models of the girls' conjoined body parts, the China Daily website reports