Twins Joined at the Chest Successfully Separated in 18-Hour Surgery Twin girls joined at abdomen survived lengthy surgery to be separated.

 -- Twin girls born conjoined at the chest and abdomen were successfully separated after an 18-hour surgery that involved 50 physicians and other medical staff.

Erika and Eva Sandoval of Antelope, California, were born joined at the lower chest and upper abdomen, referred to as omphalo-ischiopagus twins. While they were born with their heart and lungs separate, they shared some lower some anatomical structures including a liver, bladder and two kidneys.

"The twins did very well," Dr. Gary Hartman, lead surgeon and Division Chief of Pediatric Surgery at Lucile Packard Children's Hospital Stanford said in statement today. "I’m very pleased; this is as good as we could have asked for."

Eva was in the operating room for 17 hours, while her sister Erika was there for an additional hour. The twin girls are now recovering in the intensive-care unit.

Prior to the surgery, the hospital estimated there was a 70 percent chance that both girls would survive the arduous procedure.

To take on the difficult surgery, the medical team created a 3D model of the girls' shared abdomen to help guide them through the surgery. They also had their their MRI and CT scans available.

Conjoined twins are exceedingly rare and occur between every 1 in 30,000 to 1 in 200,000 live births, according to Lucile Packard Children's Hospital Stanford.