When Jacquelyn Clark found out she was pregnant with twins, her joy turned quickly to despair. Scans showed the girls were conjoined at the heart and liver. Their chances of surviving were slim.

But on Wednesday, doctors at the University of Florida Health Shands Children’s Hospital joined Clark and her boyfriend, Mark Phillips, to detail the successful separation surgery of Scarlett and Savannah Phillips.

The rare operation June 20 was aided by a high-tech, 3-dimensional printed model of the conjoined heart, smaller than the size of an apple.

“Everyone has been so caring and so helpful to us from the beginning, from the CEO to the lady who cleaned our rooms,” Phillips said during the university’s news conference. “The experience wasn’t something we planned for.”

Much about conjoined twins is still a mystery. Older studies have estimated it happens from 1 in 250,000 live births. A more recent report from 2011 puts the worldwide rate at about 1 in 68,000.

Hundreds of hours went into the successful delivery and surgery. Dozens of medical personnel, from intensive care doctors and fetal heart specialists to anesthesiologists, high-risk obstetricians and neonatal nurses, were involved in planning, rehearsing, orchestrating – and even keeping secret – the surgery.

“It took a village, literally, to separate these twins,” said Dr. Saleem Islam, who performed the liver separation. He is a professor of surgery and pediatrics in the University of Florida College of Medicine and chief of the division of pediatric surgery.

Dr. Jennifer Co-Vu, the girls’ cardiologist at University of Florida Health, said she saw the parents when they had already been told by at least two high-risk obstetricians that “based on the studies and literature, mortality is extremely high — if not almost 100 percent, as quoted by one paper — if there is connection in the heart.”

But she saw a glimmer of hope.

“The way they were connected in the upper chambers, one in the right atrium connected to the other in the left atrium, from what I saw from that moment on, we could separate babies,” said Co-Vu, clinical assistant professor in the department of pediatrics and director of the hospital’s Fetal Cardiac Program. “There was a possibility of surgery.”

The risks were still high. One or both babies could die.

Doctors told Clark two days before Christmas that her babies might live only a few hours. A month after hearing that grim news, she wrote in an online journal she kept of her experience about the glimmer of hope she received from Co-Vu.

“The doctor started drawing pictures and explaining anatomy of the hearts. She said our girls have two fully formed hearts. They are just attached,” she wrote. “She went through the whole list of pieces and parts, and they have them all. The right size, and where they are supposed to be.

“She said, they are the most complete and balanced conjoined twins not only has she ever seen, but had been able to research.”

From there, it was all about waiting. And hope.

The girls were born the morning of April 12.

Scarlett and Savannah were joined at the heart and liver.

“They came out holding onto each other, like in a hug,” Clark wrote in her journal. “And it was beyond precious.”

They were connected at the liver, diaphragm, sternum and the upper chamber of the heart, known as a thoraco-omphalopagus connection. At 2 months old, doctors operated.

One of the technologies that helped Scarlett and Savannah was considered experimental just a few years ago.

At the American Heart Association’s Scientific Sessions 2014 conference, Dr. Matthew Bramlet presented research about some of the first cases where 3-dimensional printed models of the heart were used to help surgeons treat heart birth defects.

Typically, doctors use 2D images taken by X-ray, ultrasound and MRI for surgical planning. But now, with these images as a guide, doctors can use high-tech printers to build detailed 3D models from materials such as plaster or ceramic to help give more detail and reveal even the most complicated structural abnormalities.

In two years, the use of 3-D printing in medicine is growing exponentially, moving from experimental use to breaking new ground. The models are used in surgery pre-planning, determining the best treatment, and how and where to operate.

A presentation at AHA’s Scientific Sessions 2015 discussed how a new 3-D computer modeling system could improve a surgeon’s ability to select the best sized donor heart for children receiving heart transplants.

This past December, an Australian neurosurgeon removed a patient’s cancer-riddled vertebrae and successfully replaced them with a 3D-printed body part .

Earlier this year, surgeons in Corpus Christi, Texas, used an interactive virtual 3D model of the anatomy of conjoined twins to help separate them .

Bramlet, who also is assistant professor of Pediatrics and director of the Congenital Heart Disease MRI Program said 3D printing and virtual reality surgery simulation gives a visual-spatial understanding that can take some doctors years of work and experience to develop.

It’s all about a deeper understanding.

“We’ve printed out 60 or 70 hearts, and every time I print out a heart, I learn something new about that case,” said Bramlet, director of advanced imaging and modeling for the Jump Trading Simulation and Education Center in Peoria, Illinois. “It might not change anything about the case or the diagnosis, but that little effort to go the extra mile, that’s why we are going full tilt with this. It’s raising the standard of care.”

The Jump Center is a collaboration between OSF HealthCare and University of Illinois College of Medicine at Peoria, which offers 3D technical help for doctors who call needing medical decision-making help with congenital heart issues.

“That’s what drives our research, not so much printing a heart, but how do you improve the quality and drive processes to eliminate human error,” he said. The technology is key for education and training, as well as for helping better understand the most complex of medical cases.

Mark Bleiweis, M.D., holds models of the girls’ hearts made by a 3D printer.

Mark Bleiweis, M.D., chief of pediatric and congenital cardiovascular surgery at UF Health, holds models of the girls’ hearts made by a 3D printer.

It was complexity that convinced Co-Vu that a 3D model of Scarlett and Savannah’s joined heart was critical to mapping out their case. Although UF Health has its own 3D printer, Co-Vu outsourced the job, to a printer with the capacity for more complex detail and colors.

An MRI expert, she spearheaded getting the heart printed, assuring it could be sliced and opened to view the complex systems inside. She color-coded, in neon green, the area that Dr. Mark S. Bleiweis, chief of pediatric cardiovascular surgery and director of UF Health’s Congenital Heart Center had to cut to separate Scarlett and Savannah’s hearts.

“To be able to preplan this way where you have the exact model of what you will see inside is just wonderful,” she said. “The way technology has evolved to this high level is just amazing. … Hopefully in the future, there will be ways where we could have these 3D models beat and simulate what’s happening in the patient’s heart.”

Savannah now has a normal heart and is almost ready to go home. Scarlett, who has congenital heart disease, has another heart surgery in her future. While there are risks, Scarlett’s next surgery is one that is more common.

“These babies are a miracle,” their father, Mark Phillips said in a short video played publicly Wednesday. “And we’re going to treat them like that going forward every day.”