Doctors use stem cells in womb to treat spina bifida before birth

Michelle Johnson was 20 weeks pregnant when she learned her unborn son had spina bifida. This condition meant his spine hadn't fully closed, leaving his spinal cord exposed. Without surgery, he would face lifelong disabilities.

Johnson enrolled in an experimental trial at the University of California, Davis. The treatment combined fetal surgery with stem cells to help healing.

Now four years old, her son Tobi can walk and doesn't have symptoms like loss of bladder or bowel control. Johnson called Tobi's physical and mental abilities "nothing short of a miracle."

Tobi is one of six children in the CuRe trial. This is the first study to check if using stem cells to repair tissue in fetuses with spina bifida is safe. The stem cells were delivered by a small patch sewn onto the damaged area. They protected the spinal cord from swelling and helped the wound heal. None of the babies or mothers had short-term side effects like unwanted tissue growth or cancer.

With only a few participants, it's too early to know how the treatment will work as the children grow. But because it showed promising safety, the FDA has approved more pregnant women with spina bifida to join the study.

Aijun Wang, a study author, said this is a big step for fetal therapy. It doesn't just fix the problem, but might also help heal and protect the developing spinal cord. The CuRe trial is part of a growing effort to treat diseases with stem cells before birth. This approach could slow, stop, or even cure many diseases.

Giving Babies a Head Start

Spina bifida happens when the spine or spinal cord doesn't close properly during development. About one in 2,875 newborns in the US are affected each year. In its most severe form, fluid builds up around the brain, damaging the spinal cord. This can cause lifelong movement problems and paralysis.

Doctors first treated spina bifida after birth by closing the defect. But by then, damage was already done. Surgery before birth could prevent symptoms, as shown in a 2011 trial. Still, over half of treated babies struggled to walk without help. This was likely because injured nerve cells in their brains and spinal cords didn't get a chance to heal.

Stem cells help regrowth by releasing protective nutrients. The environment inside the womb is also perfect for these cells. The team wondered if adding stem cells could improve prenatal surgery.

They started testing this idea around 2012 using induced pluripotent stem cells. These are stem cells made from skin or other mature cells. This method could provide an endless supply of stem cells, but it didn't work.

After years of trying, the team found success with stem cells from placentas. These cells protected nerve cells from injury and helped them grow in lab dishes. They also healed defects in a lamb model of spina bifida. Newborn lambs that received stem cells with prenatal surgery could stand and walk. Those who only had surgery could not.

Stem cell therapy looked promising. But for unborn babies, it could be risky. Since the cells come from donors, they might cause immune reactions. They could also trigger abnormal tissue growth or even cancer. Because stem cell treatments are rarely used in the womb, little is known about their effects on pregnancy or the health of the mother and baby.

A Landmark Trial

The first part of the CuRe trial focused on these safety concerns.

The team put stem cells from donated placental tissue onto a small patch. The patch was designed to help the cells integrate into the body.

Surgeons made a small opening in the uterus when the pregnancy was 24 to 25 weeks along. They gave the fetus painkillers and muscle relaxers. Then, they placed the stem cell patch onto the exposed spinal cord and closed the opening.

The trial closely watched six babies, including Tobi, for side effects. After delivery by C-section, none had complications like fluid leaks, infection, or signs of cancer. The treatment prevented parts of the brain from slipping into the neck. None of the babies needed a shunt, which is a tube to drain excess fluid from the brain. This was an encouraging sign of success.

The team used stem cells because they can reduce brain inflammation and brain cell death. They also produce growth proteins that support nerve tissue and spinal cord health.

The study was designed to check safety, not to see if stem cells improved surgery results. But Tobi's strong recovery is a hopeful sign that the cells do make a difference. Since spina bifida is a structural problem, treating it before permanent damage could make the therapy a "one-and-done" fix.

This study adds to the growing use of prenatal stem cells for conditions like thalassemia, a blood disorder, and osteogenesis imperfecta, also known as brittle bone disease. Early trials show promise, but regulators haven't approved any treatments yet.

Diana Farmer, a study author and lead investigator for the CuRe trial, said putting stem cells into a growing fetus was a complete unknown. She is excited to report great safety. This opens the door for new treatments for children with birth defects.

The team is now recruiting more pregnant women for the trial's second phase. They will track the children's growth and health up to age six. This will assess brain and cognitive development, motor skills, and other milestones.

If the treatment works, longer monitoring might be needed. Spina bifida can increase the risk of kidney disease and certain cancers later in life. It's unclear if the stem cells could cause problems months or years later.

Despite these unknowns, Johnson is happy to be part of the trial. She said her family is grateful for the health professionals who supported Tobi's journey and continue to watch him succeed.

Deep Dive & References

• First-ever in-utero stem cell therapy for fetal spina bifida repair is safe, study finds - UC Davis Health, 2026
• In-utero stem cell therapy for myelomeningocele: a first-in-human phase 1 trial (CuRe) - The Lancet, 2025
• Management of Myelomeningocele Study (MOMS) - New England Journal of Medicine, 2011
• Human Placenta-Derived Mesenchymal Stromal Cells Protect Against Neural Injury in a Rodent Model of Myelomeningocele - Journal of Pediatric Surgery, 2021
• Human placenta-derived mesenchymal stromal cells protect neurons from injury and promote their growth - FASEB Journal, 2019
• In Utero Stem Cell Transplantation in Patients with Thalassemia - Blood, 2020
• An exploratory open-label multicentre phase III trial evaluating the safety and efficacy of in utero stem cell transplantation in patients with severe osteogenesis imperfecta - Lund University, 2021