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Results from a large study show that fetal surgery on the spine can produce better outcomes for children with the spine defect spina bifida, and shows a clear benefit over waiting until the child is born to perform the surgery.

In the past, both pregnant women and doctors alike were afraid of the surgery, which involves fixing a hole in the spine of a child while it is still in the womb. Pushes from the government wanting evidence of safety and successful outcome led hospitals to stop performing the surgery altogether.

"This is the first hope for spina bifida fetuses," said lead researcher Dr. Scott Adzick of Children's Hospital of Philadelphia, one of three places that participated in the study.

Doctors started experimenting with fetal surgery for spina bifida in the mid-1990s, cutting into the mother's abdomen and uterus to close the gap in the spine. It even became part of the abortion debate when a photo of a tiny hand poking out of a womb during surgery was published.

The government-funded study showed that babies who have the operation in the womb were more likely to walk without help and less likely to need a tube to drain fluid buildup in the brain. Fetal surgery did come with some risks, however, including a higher chance of being born premature and complications for the mother.

Spina bifida — which means split spine — happens when the spine doesn't develop properly. In the most severe cases, the spinal cord sticks out through an opening in the spine. Children often are paralyzed or have weakness below the waist and many need crutches or a wheelchair. They also suffer from incontinence and fluid buildup in the brain.

Cases in the U.S. have dropped to 1,500 a year since 1998, when the government ordered that foods like cereals, breads and pasta be fortified with folic acid, which reduces the risk of the spinal defect.

Though spina bifida is usually diagnosed before birth, the operation is typically done days after delivery. Quick surgery can prevent further harm but cannot reverse the nerve damage that has already occurred.

When fetal surgery for spina bifida was first tried, it was controversial because operations in the womb were typically done for life-threatening problems. There was also no long-term research on the safety of the surgery. The operation even got caught up in the abortion debate when abortion opponents seized on a photo taken during surgery on a 21-week-old fetus at Vanderbilt University.

By the end of 2002, more than 230 spina bifida operations had been done, but some doctors remained skeptical. So the National Institutes of Health launched a big study that year at Vanderbilt, the Philadelphia hospital and the University of California, San Francisco. Other hospitals agreed not to do the surgery while the research was under way.

The researchers, whose findings were published online Wednesday in the New England Journal of Medicine, studied 158 babies who had the surgery either in the womb or after delivery. The fetal surgery was done between 19 and 25 weeks of gestation.

By the time they turned a year old, 40 percent in the fetal surgery group needed a drainage tube, or shunt, in the brain, compared with 82 percent in the standard surgery group. The fetal surgery group scored higher on combined tests of mental development and motor skills at 2 1/2 years, though there was no difference in cognitive function alone.

Forty-two percent of the toddlers in the fetal surgery group could walk without crutches or other support versus 21 percent in the other group.

Two children died within days of the fetal surgery; two children who had the fix after birth and had shunts died later.

Eighty percent of those who had fetal surgery were born premature compared with 15 percent in the after-delivery group. On average, children who had surgery while still in the womb were born 1 1/2 months early and had more breathing problems. A third of the mothers who had the operation had thinning in the wall of their uterus, a complication that requires cesarean delivery in the future.

"Not all the patients were helped here, and there are significant risks," said pediatric surgeon Dr. Diana Farmer of UC San Francisco. "So this procedure is not for everyone."

For safety reasons, the study did not include obese women, even though they have higher rates of fetuses with spina bifida.

Since fetal surgery is highly specialized, some experts said that the results may not be as good in hospitals with little experience and that more work is needed to better determine who will benefit most.

"Caution is necessary here," Dr. Joe Simpson of Florida International University and Dr. Michael Greene of Massachusetts General Hospital wrote in an editorial.

It was a grueling ordeal for many expectant mothers in the study. Many who had the fetal surgery needed to move near the surgery center in case they delivered early. The editorial writers noted that only 15 percent of those who expressed interest in the study chose to participate. Others were either ineligible or did not want to take the risk.

Seven years after fetal surgery, Evan Terrell of Nashville, Tenn., is more active than his parents ever hoped. He swims, rides his bike and plays basketball with his friends. Soon after birth, Evan went through intensive physical therapy to strengthen his legs. He needed braces and inserts in his shoes to help him walk as a toddler, but no longer requires any assistance.

His mother, Kristie Terrell, who participated in the study at Vanderbilt and stayed in the hospital for a month, said she is thankful that he didn't need a shunt in his brain.

"He is a bouncing, hyper, beautiful boy," she said.

Vanderbilt performed the first fetal surgery for spina bifida in 1997 on Daniel Meyer, at 29 weeks. Today, the technique is done earlier in pregnancy.

Now 13, Daniel uses a wheelchair, but that doesn't stop him from going fishing and playing tennis and basketball, according to his mother, Cory Meyer.

Daniel had an operation last year to replace the brain tube put in after he was born. He also has some bladder problems but is otherwise healthy.

"I'm totally happy with the decision that we made" to have fetal surgery, said the boy's father, Scott Meyer. "I think it's helped out a lot of kids."

The Associated Press contributed to this story.