Six Babies Got Stem Cells Before They Were Born. Here's What Happened.

Between July 2021 and December 2022, six pregnant women at UC Davis underwent fetal surgery for spina bifida. Standard procedure: open the womb, repair the baby's exposed spinal cord, close everything up.

But before the surgeons closed, they did something nobody had ever tried on a human fetus. They placed a patch of stem cells — derived from donor placentas — directly onto the baby's exposed spinal tissue.

Last week, The Lancet published the results. All six babies are safe. No tumors. No infections. No complications from the stem cells. And there are early signs the treatment might work better than surgery alone.

What Spina Bifida Does

Spina bifida happens when a fetus's spine doesn't close properly during early development. The spinal cord stays partially exposed. It's the most common neural tube defect, affecting roughly 1 in every 2,500 births worldwide.

The consequences are lifelong. Paralysis. Difficulty walking — or inability to walk at all. Bladder and bowel problems. Many children need brain shunts to drain excess fluid. Cognitive challenges are common.

For decades, the only option was surgery after birth to close the opening. Then, about 15 years ago, prenatal fetal surgery became the standard. Operating before birth — typically around 24 to 25 weeks of gestation — produces better outcomes than waiting. The landmark MOMS trial in 2011 proved it.

But "better" still isn't "good." Most children who receive prenatal surgery still can't walk independently. The nerve damage happens progressively as the exposed spinal cord sits in amniotic fluid. Surgery stops further damage. It doesn't reverse what's already happened.

That's the gap stem cells might fill.

How the CuRe Trial Works

Diana Farmer, chair of UC Davis's Department of Surgery and the trial's principal investigator, had been working toward this moment for over a decade. Her team tested the approach in animal models first — sheep and dogs with spina bifida-like conditions. The animals showed improved mobility after receiving stem cells during fetal surgery.

The human trial — called CuRe (Cellular Therapy for In Utero Repair of Myelomeningocele) — used placenta-derived mesenchymal stromal cells. These cells are known for three things: reducing inflammation, promoting healing, and protecting nerve tissue.

Here's how it worked. Surgeons performed standard open fetal repair on six babies at 24 to 25 weeks of gestation. Before closing the wound, they applied stem cells seeded onto an FDA-approved extracellular matrix — basically a biological scaffold — directly onto the exposed spinal cord.

Then they waited.

What Happened

"Putting stem cells into a growing fetus was a total unknown," Farmer said. "We are excited to report great safety."

The Phase 1 results:

All six babies were born with spinal repairs intact. Zero infections. Complete wound healing across the board. No signs of tumors or any complication that could be linked to the stem cells.

MRI scans showed all six newborns experienced reversal of hindbrain herniation — a key indicator that the surgery worked as hoped. Hindbrain herniation is when part of the brain gets pulled downward through the opening at the base of the skull, a common and dangerous feature of spina bifida.

None of the six babies needed a shunt for hydrocephalus before leaving the hospital. That's remarkable. Brain shunts are one of the most common interventions for children with spina bifida, and avoiding them is a major quality-of-life improvement.

And leg motor function showed improvement.

The Honest Caveats

This was a Phase 1 trial. Six babies. No control group. It was designed to answer one question: is this safe? The answer appears to be yes.

Whether stem cells actually improve outcomes beyond surgery alone — that's a Phase 2 question. The trial is now expanding to enroll more patients, with a proper comparison group.

Six is a tiny sample. The babies were treated in 2021 and 2022, so the oldest are about four years old now. Long-term data is still coming. The treatment requires open fetal surgery at a specialized center — there are only a handful of hospitals in the world equipped to do this.

And stem cell therapies have a complicated history. For every legitimate trial like this one, there are unregulated clinics charging desperate patients for unproven treatments. The CuRe Trial is the opposite — rigorous, FDA-approved, peer-reviewed in The Lancet. But the hype machine around "stem cell breakthroughs" means the distinction matters.

Why It Matters Anyway

Here's the thing: this isn't just about spina bifida.

The CuRe Trial is the world's first successful delivery of a living cellular therapy to a human fetus. If in-utero stem cell treatment works for spinal cord repair, the same approach could eventually apply to other conditions diagnosed before birth — other neural tube defects, genetic disorders, organ development problems.

Researchers outside the trial called it "a milestone for efforts to use in utero stem cell treatments for birth defects more generally."

Farmer's team spent a decade on animal studies before touching a human patient. The FDA approval process was meticulous. The results, while preliminary, are clean. This is how medical breakthroughs are supposed to happen — slowly, carefully, transparently.

What Comes Next

Phase 2 is underway. More patients, a control group comparing surgery-plus-stem-cells against surgery alone. Results will take years.

If the data holds, the next challenge is access. Fetal surgery for spina bifida already requires a level of medical infrastructure that most of the world doesn't have. Adding stem cell therapy makes it more complex, not less.

About 300,000 babies are born with neural tube defects every year worldwide. The vast majority are in low- and middle-income countries where prenatal diagnosis itself is often unavailable, let alone fetal surgery.

That's the gap between a breakthrough and a solution. The science worked in six babies at one of the best-resourced hospitals on the planet. Making it work for the 300,000 is a different problem entirely.

But it starts here. Six babies. Six patches of stem cells. Zero complications. And early signs of something that could change how we treat one of the most common birth defects in the world.

That's worth paying attention to.