(CNN) — These sisters share a special bond, one that has received attention worldwide.
After almost 11 months of being attached to each other by their waists, Ximena and Scarlett Hernandez-Torres have been successfully separated, according to their mother, Silva Torres. They were expected to endure 12 to 18 hours of surgery on Tuesday at a hospital in Corpus Christi, Texas. At 7 p.m. ET, Torres said on her Facebook page they were still in surgery.
“A dedicated team of specialists has been working for months to prepare for this complex surgery,” said pediatric surgeon Haroon Patel, who heads up the team undertaking the marathon procedure.
The occurrence of conjoined twins happens once every 200,000 births and about 70% of conjoined twins are female. The overall survival rate of conjoined twins is somewhere between 5% and 25%, according to the University of Maryland Medical Center.
The twins were born in Corpus Christi on May 16, 2015, as part of a triplet set. Their sister, Catalina, was born without any serious health issues. The family set up a Facebook page to publicly share Ximena and Scarlett’s journey to separation.
According to Driscoll Children’s Hospital news release, the chance of a triplet birth involving conjoined twins is 1 in 50 million.
The conjoined babies were connected below their waists and shared a colon and bladder. These organs will be reconstructed after the girls are separated surgically. A team of doctors at Driscoll Children’s Hospital in Corpus Christi attended to the twins this past year, prepping them for the procedure.
“This is an extremely challenging operation, but we look forward to a successful outcome,” Patel said in a statement before the surgery. The hospital has not yet released a statement on the outcome of the procedure.
This is a historic moment for the Texas hospital as well. This is the first time they have separated conjoined siblings.