One of the conjoined twin girls separated from her sister in a lengthy operation last week is apparently in a critical condition.

The 11-month-old twins underwent almost 13 hours of highly complicated surgery at Fudan University’s Children’s Hospital in Shanghai under the care of 70 doctors and nurses working in shifts.

While her sister Chen Jingni is breathing with the help of a respirator and in a stable condition, Hu Jingxuan’s condition is reportedly unstable and she remains under emergency treatment in an intensive care unit.

The twin girls who are from the eastern province of Zhejiang, had shared a liver and a digestive tract before the surgery and had congenital heart disease.

Gui Yonghao, president of the Shanghai hospital says the twins’ deformity was very rare, and this was the first separation surgery of its kind in the world.

Gui Yonghao says it will be a miracle if one child survives and a challenge to the limits of medicine for both to survive.

Despite the success of the surgery the twins still face potentially fatal challenges such as organ failure, infection, blood disorders and nutritional problems. Both have congenital heart conditions and will require more surgery.

In an attempt to guarantee the success of the operation, the hospital halted all elective procedures and placed its entire staff of experts on call.

A team of 27 doctors, seven anesthesiologists and eight nurses began the delicate procedure to decouple the girls, joined from the upper chest to the lower pelvis. Surgeons had to separate the infants at the bladder, uterus, pelvis, intestines, liver and the sac that covers the heart.

The girls were finally freed from each other at 5:20pm, and surgeons then began the task of repairing their tissues.

Meanwhile conjoined twins, who were born on July 3 in Bangladesh’s capital Dhaka, died at Dhaka Medical College Hospital (DMCH) early Friday, due to respiratory problems according to Professor Kabirul Islam, head of the Department of Paediatric Surgery at the DMCH.

A 27-year-old mother gave birth to the female twins who were joined at their chest and abdomen.

An ultrasonography test of the newborns found that the twins had one liver, one rectum, two kidneys instead of four and one urinal bag instead of two.

Professor Kabirul said the conjoined twins were improving but died due to infections possibly from the people gathered around the hospital bed who touched them.