HOUSTON » Doctors in Houston are optimistic that 10-month-old formerly conjoined twin girls will survive after a recent surgery that separated them.

It took 26 hours last week to separate the girls, Knatalyne Hope Mata and Adeline Faith, who shared a chest wall, lungs, a part of their heart lining, diaphragm, liver, colon, intestines and pelvic area, according to lead surgeon Dr. Darrell Cass. The surgery, which took place at Texas Children’s Hospital in Houston, had been planned since before they were born last April.

"The surgery was not without its challenges, with the girls sharing several organ systems, but we’re very pleased with how they’re doing," Cass told the Houston Chronicle for a story published Monday. "We’re very optimistic they can both have a really great outcome."

The girls were in stable but critical condition, will be on ventilators for the next week and are expected to be in intensive care for a couple of months, then have more surgery later.

Cass said about five hours into the operation, Adeline’s blood pressure dropped to where the surgical team needed to manually pump her heart to resuscitate her. She recovered after about five to eight minutes.

"It seemed forever at the time," Cass said.

The surgical team included eight nurses, six anesthesiologists and 12 surgeons.

The twins’ mother, Elysse Mata, and her husband, John, moved from Lubbock to Houston last year to be near their daughters. She said they were "so grateful to all of the surgeons and everyone who cared for our daughters and gave them the incredible chance to live separate lives."

"We know how much planning and time went into this surgery and we are so blessed to be at a place like Texas Children’s where we have access to the surgeons and caretakers that made this dream a reality," she said in a statement released by the hospital.

The couple also has a 5-year-old son.

The conjoined condition of the girls was discovered during a routine ultrasound in January 2014. Each weighed 3 pounds, 7 ounces at birth. They have since been in the hospital’s neonatal intensive care unit and grown to more than 20 pounds.

"Seeing the girls wheeled out of the operating room as separate patients, on separate gurneys, the ramifications for them to live private lives was even more poignant and powerful than I expected," said Cass, co-director of Texas Children’s Fetal Center and associate professor of surgery, pediatrics and obstetrics and gynecology at Baylor College of Medicine. "It literally brought tears to my eyes."