There’s about a one in 2.5 million chance that babies will be born conjoined at the head. Anias and Jadon McDonald are that rarity, and on Thursday, a team of doctors will attempt to separate the 13-month-old twins in a lengthy, extremely complicated surgery.

According to CNN, which is closely following the surgery on Facebook Live, the boys were wheeled into the Children’s Hospital at Montefiore Medical Center in the Bronx, a little after 7 a.m. ET on October 13 for the start of what could be a 20-hour-surgery. Their parents, Nicole and Christian McDonald will be waiting the whole time.

The pair, who live in Braidwood, Illinois, found out that their children would be conjoined during an ultrasound in May of 2015. Anias and Jadon are what’s known as craniopagus twins. About 40 percent of craniopagus twins are stillborn, and up to 80 percent die before they turn two. Especially given the practical complications and severe limitations the boys would endure throughout their lives, the choice to attempt to separate them was hard, but necessary.

It’s going to be risky, since they share 1.5 to 2 inches in diameter of brain tissue between them. It’s a very real possibility that one, or both of them, could suffer brain damage — or death.

“We know that is definitely a real possibility, but we’re still going to love our boys,” Christian told CNN.

Jadon and Anais prior to the surgery.
Jadon and Anais prior to the surgery.

Dr. James Goodrich, perhaps the leading expert in this high-stakes, niche field of medicine, will lead the surgery. He’s separated seven sets of twins already, and seems like kind of a badass. The 70-year-old doctor told CNN that separating conjoined twins is “actually pretty awesome.”

“It’s chaotic,” he continued. “You’re trying to get two kids on two tables … The problem is when you have nothing holding the brain in, the brain can actually slip and fall out. So, it’s quite a treat to get them repositioned.”

New technology has allowed experts to make 3D maps of the twins’ brain tissue, meaning this is one of the most advanced separation operations ever attempted.

Anias and Jadon have already had three operations leading up to the $2.5 million surgery, so that doctors could insert tissue expanders into their heads to make it so there’d be enough skin to reconstruct the tops of their heads afterward.

“This is about as complicated as it gets,” Goodrich said.

Photos via YouTube/CNN (1, 2)

James Grebey is a writer, reporter, and fairly decent cartoonist living in Brooklyn. He's written for SPIN Magazine, BuzzFeed, MAD Magazine, and more. He thinks Double Stuf Oreos are bad and he's ready to die on this hill. James is the weeknights editor at Inverse because content doesn't sleep.