Born joined at the head, twins can now sit side by side. Next stop: home.

Fifteen months after they were born joined at the head, twin girls from Mooresville are nearing another milestone in their young lives: going home.

Erin and Abby Delaney have known nothing but hospital life, and their extended family includes the staff at Children’s Hospital of Philadelphia. One nurse ran a mile and a half in a downpour just to say goodbye before the girls went into the June 6 surgery that separated them.

The 11-hour surgery, performed by an interdisciplinary 30-member team, was exceedingly rare. Doctors at CHOP, founded in 1855 as the nation’s first pediatric hospital, had previously separated 23 conjoined twins, more than any other hospital in the Western world.

But never a pair joined at the head, a condition called craniopagus that occurs in only 2 percent of such cases. Conjoined twins occur once in every 50,000 to 60,000 births. Most are stillborn.

Parents Heather and Riley Delaney learned from a prenatal ultrasound that their twins were conjoined.

“That was a very scary day,” said Heather Delaney, 27, who is a former nanny. “It’s one of those things that when it’s told to you, (you think) it’s something that happens on TV, it doesn’t happen to normal people.”

A later scan showed the girls had separate brains. Erin and Abby would be joined mostly by bone and the skin covering their heads. Doctors at CHOP thought the children could be safely separated.

In late June 2016, Heather Delaney went to CHOP and has been in Philadelphia since then. Her husband, Riley, 24, continued to work for the e-cigarette company Madvapes but visited every month to six weeks, driving 10 to 11 hours each way.

The babies were born 10 weeks premature, in July 2016, each weighing 2 pounds 1 ounce.

Fear and confidence

For the first couple of weeks after their birth, Heather Delaney could only change diapers and cuddle them in skin-to-skin “kangaroo care.” It took two people to cradle the babies.

Three months after their births, doctors started moving the girls apart in a process called “distraction,” a technique used in other kinds of reconstructive surgery but new to separating conjoined twins.

Surgeons cut through the bone where their skulls met and placed a device that would gradually push them apart. The nearly 1 inch of separation gave surgeons more room to work when they were finally separated.

More procedures followed, including placement of tissue expanders below the skin where their foreheads joined. Like water balloons filled with saline solution, the expanders slowly stretched the skin to cover the gap when the twins were separated.

Physical and occupational therapists devised ways to help the girls develop while conjoined, including a specially-built swing for two. But as the separation surgery date drew closer, the twins’ parents toggled between confidence in the surgical team and fear of the outcome.

“You don’t know if they’re going to come back,” Heather Delaney said recently. “And if they do come back, you don’t know how they’re going to come back.”

Riley Delaney heard “Da-da,” first by Erin and then Abby, before the separation surgery.

“That was a huge thing for me. To me, that’s incredible,” he said. “I guess it reassured me that they were going to be OK.”

3-D roadmaps

The surgery began early the morning of June 6. Three-D printers had created roadmaps of the girls’ skulls, blood vessels and skin to guide surgeons. Computer-assisted surgical navigation, which works something like the GPS in your car, would track the movements of special instruments.

Surgery began with hours of work to separate the blood flow between the girls, the membrane covering their brains and the small amount of brain tissue they shared. Halfway through, the surgeons flipped the girls to repeat the process on the other side.

The surgical team faced an unusually daunting problem throughout the day: what it did to one baby affected the other.

Particularly stressful was separating a large vessel that carries blood from the brain to the heart, said Dr. Gregory Heuer, the pediatric neurosurgeon who co-led the team. If bleeding wasn’t stopped quickly, the babies could die.

At 8:43 that night, the separation was complete.

The girls were missing much of the skin on the tops of their heads and the tough, outer membrane that covers the brain, said Dr. Jesse Taylor, the plastic and reconstructive surgeon who co-led the team with Heuer. Synthetic material replaced the membrane, called the dura. The skin that had been stretched before surgery was then sewn into place.

Months of therapy in the hospital’s rehabilitation wing followed. The twins had to adjust to their separation, including learning how to sit up for the first time. As they grow, the girls will need more surgeries to replace missing bone at the tops of their heads, adjust their hairlines and minimize scarring.

But doctors say both girls are doing well. Erin was recently discharged but remains in Philadelphia. Abby, who was treated for a blood infection, is still at the hospital.

‘Enjoy every snuggle’

Despite the sterile surroundings far from home, parents and twins bonded into a family at the hospital.

“They let me hold them a week after separation, and I’ve been snuggling ever since,” Heather Delaney said.

“They could fit in my shirt. I tried to remind myself, even though they were in the hospital, to just enjoy every snuggle, every coo, every cry. I’ve just tried to enjoy it all because I knew they’ll never have those baby days back again.”

Each of the identical twins has a distinct personality, one loud and the other quiet.

“Erin is a spitfire,” Heather Delaney said. “That little girl will let you know she’s in the room. Abby will analyze something for half an hour. She wants to make sure it’s done correctly.”

Surrounded by toys and dancing in their beds, “they’re very, very happy girls,” she said. The twins got more than 300 cards from around the world on July 24, their first birthday.

Heuer, the neurosurgeon with a daughter at home, allows himself to favor Abby. Once the twins were separated in surgery, he said, much of Abby’s blood went to Erin. Abby endured more swelling after surgery and a longer stay in intensive care.

“There’s something about the look in her eyes,” Heuer said. “They’ve always been separate kids, even when they were connected.”

Once back home in Mooresville later this year, there will be visits by therapists, appointments to keep and many unknowns.

There’s even a question of where home will be. Riley Delaney has lived with his in-laws and his wife at the Ronald McDonald House at CHOP for families of seriously ill children. They family will initially stay with Heather Delaney’s parents but plan to buy a house in Mooresville.

There’s also the question of how to pay for medical care that Riley Delaney estimates is “well into double-digit millions.” Heather Delaney didn’t have insurance when she got pregnant, but Medicaid now covers the girls. A GoFundMe page (www.gofundme.com/Delaneytwins) for the twins has raised $25,000.

“I think these kids are set up to do great when they go home. Heather is a great mom,” Heuer said. “What I wouldn’t do right now is put any limitations on how good their outcomes are going to be.”

Heather Delaney, who has documented her girls’ journey on a blog (delaneytwins.weebly.com/) and on Facebook since before they were born, has a simple wish for her children:

“I’ve always said my hope is just that they’re happy, whether or not they have deficits. Going to school, having friends. Just being happy.”

Bruce Henderson: 704-358-5051, @bhender