LONDON — When Zainab Bibi gave birth to her eighth and ninth children — twin girls — it was five days before she was well enough to be introduced to them. All she knew was that they had both had survived the cesarean section and were healthy.
At the hospital in Peshawar, Pakistan, she was given a photograph to prepare her for the discovery to come: The girls were conjoined at the skull. Surgery to separate them, she was later told, would almost certainly end one of the girls’ lives.
“They were very beautiful and they had nice hair with white skin,” Ms. Bibi told the BBC. “I didn’t even think about the fact they were joined. They are God-given.”
The thought of losing one of them was unfathomable.
That was in the winter of 2017. A potential solution appeared three months later, when the family was introduced to Noor ul Owase Jeelani, a neurosurgeon at Great Ormond Street Hospital in London, where teams of specialists have successfully treated two similar cases since 2006.
On Monday, the hospital announced that the twins, Safa and Marwa Ullah, had been successfully separated after more than 50 hours in surgery since last October, and thanks to the work of a team of 100. The final operation was completed in February, and it took until July 1 for the girls to be well enough to leave the hospital.
Until the operations were complete, the girls had never seen each other’s faces.
The two years between their birth and their separation were spent getting British visas, organizing travel and gathering funding for the series of surgeries that would allow them to live fully independent lives.
In multiple operations, surgeons separated the brains and the blood vessels intertwined in the girls’ conjoined skulls. Then, they inserted a piece of plastic between the two brains to complete the separation internally. Finally, the surgeons worked on stretching the skin and building separate skulls with the girls’ own bones.
Funding for the operations came from a donor who has not been publicly identified. But the team relied on more than 1.3 million pounds (more than $1.6 million) invested in the past six years into Great Ormond Street’s craniofacial surgery program and research.
Safa and Marwa Ullah’s condition was extremely rare. Conjoined twins occur in only one in 2.5 million cases, and only 5 percent are joined at their skull, according to the hospital. Less than half of those survive more than a day after birth.
Programs to help children with such conditions exist in only a few hospitals worldwide. Saudi Arabia has a long-running program to help children in similar situations from around the world. Since 1990, a team there has performed 40 procedures for families from 20 countries.
Great Ormond Street Hospital has a specialist operating theater for surgery on conjoined twins, and the series of operations on Safa and Marwah Ullah were supported by a team of scientists and designers.
The team used a virtual-reality replica of the girls’ skulls to understand the relationships between the girls’ brains and blood vessels and come up with the best strategy to separate them. They created 3D models to practice the surgery and develop cutting guides.
The hospital then worked with physiotherapists and dietitians, among others, to help the girls recover and prepare for their lives in individual bodies.
“I would be optimistic that by their third birthday they should be walking,” Dr. Jeelani said.