“She wants Eric Church on the Pandora,” Dr. Michael Belfort told the team that was preparing a woman for surgery at Texas Children’s Hospital, in Houston.

The country music fan was Lexi Royer, who, 24 weeks and two days pregnant, was about to have her belly sliced open and her uterus lifted out (though still attached internally). It would then be drained of amniotic fluid, pumped full of carbon dioxide and pierced so tiny slits could admit a light, a camera and surgical tools.

The tools would be used to repair a severe spinal defect — spina bifida — in her unborn son. It is a disabling condition, and the hope was that the operation would give him better odds of being able to walk and avoiding fluid buildup in his brain.

In a few decades of reporting on medicine, I’ve been in the O.R. during brain surgery, cesarean sections, liver transplants, cardiac bypass, an eyeball cut out of its socket — but never an operation on a fetus.

I learned about this one when I contacted Dr. Belfort about a YouTube video in which he described the need for tiny tools to operate on fetuses. He’s got a book full of his own detailed drawings — a cross between Leonardo and Rube Goldberg — of instruments he wants made. In our conversation he mentioned spina bifida surgery, and I wanted to see it. Permission was not immediate: Doctors, patients and hospital officials had to consent. Once they agreed, a public relations person was assigned to accompany me and a photographer in the operating room.

Before the operation started, one of the surgeons who would assist, Dr. Oluyinka O. Olutoye, shared a sobering thought about the potential risks of performing surgery on two patients at once. “Fetal surgery,” he said, “is one of the few operations with a 200 percent risk of mortality.”

Operating rooms are usually kept cool, almost chilly. But not for fetal surgery. If the temperature is too low, the fetus’s heartbeat can slow down too much, so this operating room was pretty hot. When the photographer, Béatrice de Géa, and I were changing into scrubs in the women’s locker room, a nurse warned, “It’s going to be like a sauna in there.”

It was crowded, too. Besides Dr. Belfort and a pediatric neurosurgeon, Dr. William Whitehead, there were two anesthesiologists, a pediatric cardiologist and two doctors who would steady the uterus and help to gently hold the fetus in position, as well as several nurses.

For reporters in the operating room, the job is to see what’s going on, stay out of the way and not touch — or even get near — anything draped in blue, which is the sterile stuff. It’s O.K. to look over the surgeons’ shoulders as long as you don’t brush their gowns. And the reporter has to stay out of the photographs, too.

In this case there were amazing views of the surgery, on three flat screens that showed images from the camera inside the uterus. Because the doctors were operating through the tiny slits, they needed those images to see what they were doing.

People often ask if I’ve ever felt sick or faint in an operating room. So far, no: What’s going on is invariably so interesting, and I’m so caught up in trying to understand it, that squeamishness just doesn’t happen. I don’t like the smell: Surgeons seem to cauterize everything they cut, and burning flesh has an acrid odor, but either it doesn’t last or my nose gets used to it.

At 9:28 that Tuesday morning, the soft Pandora music had moved on from Eric Church to Neil Young’s “Harvest Moon,” and he was singing, “I want to see you dance again,” as Mrs. Royer’s son came into view. He seemed to be kneeling inside her womb; we could see his bottom and the soles of his feet, impossibly small.

The operation was an endurance test for the surgeons. They stood shoulder to shoulder for hours, hands and arms in the air as they worked through the slits, painstakingly snipping tissue, stretching it over the open spine and stitching it shut to make a watertight seal. The spinal defect was so big that there seemed barely enough skin to cover it, and it was painful to watch it being tugged into place.

The room was so hot that I took off a gown I’d been given to put over my scrubs, and I found a chair to sit in periodically, to give my legs a break. There were no breaks for the surgeons.

Israel Kamakawiwoʻole was singing “Over the Rainbow” as the last stitch went into the fetus. By noon, the surgeons were done.

“I sweat like hell,” Dr. Belfort said, peeling his gloves off pale waterlogged hands that looked as if they’d spent too long in the bath.

Mrs. Royer’s husband, Joshuwa, his mother and Mrs. Royer’s parents were waiting anxiously, and crowded into a small room when Dr. Belfort arrived.

“Everything went very well, so you can relax,” he said, showing them pictures of the fetus’s back, before and after. “So far, so good. Now we have to hope and pray she doesn’t go into preterm labor.”

Mr. Royer was stoic, but the parents, the reporter and the photographer all burst into tears and hugged one another.

Later, Mrs. Royer’s mother, Raquel Bourgeois, said the family understood that the operation was not a cure, and that her grandson would almost certainly have some degree of disability.

“But we’re strong believers in God, and we’re at peace,” Mrs. Bourgeois said. “This baby is going to be so loved. We just don’t care.”

She went on: “Lexi and Josh are very strong together. This is not going to break them. They are the best possible parents for this child in this situation.”

I am wishing the best for Mrs. and Mr. Royer and their son, and I hope to report on how they’re all doing after he’s born.