Etched in the memories of Dennis and Melinda Stover is the day they learned their baby would be born with spina bifida.

It was January, and Melinda, a 26-year-old-bank teller from Murfreesboro, Tenn., was 20 weeks pregnant. She was having an ultrasound exam because they already had two girls ``and if it were a boy, we had a lot of stuff to buy,'' said Dennis, a 31-year old surgeon's assistant. No matter what the exam might show, abortion was unthinkable: ``We're born-again Christians.''

What it did show was that their fetus had spina bifida, a defect in which the spinal canal fails to close around the spinal cord. (Spina bifida affects 1 in 2,000 newborns and can often be prevented by taking folic acid -- found in multivitamins and some fruits and cereals -- from the onset of pregancy.)

Many children with spina bifida have such severe neurological damage that they need braces to walk and have problems with bladder and bowel function. Most also develop hydrocephalus, or excess fluid in the brain, which requires repeated operations to implant shunts to drain fluid into the abdomen.

Beyond the enormous human cost, the economic cost of caring for such a child is ``astronomical,'' notes Dr. Arnold Cohen, a former perinatologist who is now corporate medical director for women's health at Aetna US Healthcare in Blue Bell, Pa.

So the Stovers decided to take an unusual chance. They live just half an hour from Vanderbilt University Medical Center in Nashville, where over the last two years Dr. Joseph P. Bruner, director of fetal diagnosis and therapy, has done 53 experimental operations on fetuses to correct spina bifida.

This kind of dramatic surgery is so new and requires such specialized surgical teams it is done only at Vanderbilt and two other centers -- Children's Hospital of Philadelphia and the University of California at San Francisco -- though others are gearing up to do it. It also raises a number of medical, ethical, and insurance issues, partly because there are no long-term data.

The operation Melinda Stover had at 23 weeks of pregnancy is conceptually simple. Through a Caesarean section, the uterus is pulled up and placed on the woman's abdomen. A tiny incision is made in the uterus, so the amniotic fluid that bathes the fetus can be withdrawn through a needle and stored in the operating room to be put back later.

The uterus is then cut open and the fetus exposed so doctors can close the gap over the spinal cord. By closing the gap before birth, doctors reason, the spinal cord can be protected from physical trauma as the fetus bumps around in the uterus and from toxic compounds in the amniotic fluid. Closing the gap before birth also appears to reduce the risk of hydrocephalus.

Although the Stovers' daughter, Meghan, was born with club feet and no muscle function below her knees, her bowel and urinary functions are intact and the family has no regrets about the surgery. In fact, they're ``thrilled to death'' with Meghan, who was born in April. ``We could not be happier,'' Dennis Stover says.

Cohen of Aetna calls this type of surgery nothing short of ``miraculous.'' While many insurers -- including the Stovers' -- balk, Cohen was so awestruck after watching an operation, he convinced Aetna to contract with Vanderbilt to pay for patients to have the procedure, which costs about $35,000.

``It intuitively makes sense'' as a way of reducing the need for repeat operations and expensive long-term care, he said.

Though a few doctors experimented with fetal surgery in the 1960s, it was not until the early 1980s that, after numerous experiments in animals, Dr. Michael Harrison, director of the fetal treatment center at UCSF, began operating on fetuses with life-threatening tumors that inhibit lung growth and others that grow at the base of the spine, sapping the fetus' blood supply.

Back then, ``it only seemed justifiable'' to attempt fetal surgery for such potentially fatal problems, says Dr. N. Scott Adzick, director of the center for fetal diagnosis and treatment at Children's Hospital of Philadelphia.

In fact, nobody would have considered exposing the mother and fetus to the rigors of surgery for a non-fatal problem like spina bifida for the very reason that the gap over the spinal cord can be closed and a shunt can be implanted to treat hydrocephalus after birth.

And the risks of fetal surgery to both mother and fetus are considerable, including the chance that in the weeks afterwards, the uterus can contract so much the baby will be premature or even stillborn. To prevent this, mothers are now given drugs such as magnesium and terbutaline until it's time -- at about 34 weeks of pregnancy -- to deliver the baby by another C-section.

(C-sections are necessary because fetal surgery creates a fresh uterine wound; with vigorous contractions during labor, that wound could rip, jeopardizing both mother and fetus.)

By the mid-1990s, Bruner decided it was time to try fetal surgery on fetuses with non-lethal malformations. He operated on four fetuses with spina bifida.

``It was an unmitigated disaster,'' he says. His team worked endoscopically -- not through a big incision in the woman's abdomen as he does now, but through tiny incisions through which instruments and a TV camera were inserted. Although surgeons now use endoscopic fetal surgery for other malformations, Bruner's tiny spina bifida patients did not fare well with this approach; two died and two were born prematurely.

So Bruner switched to the open procedure, and the results, he says, are encouraging, though he concedes it's not yet clear whether the surgery increases the chance that a child with spina bifida will walk.

But while most babies born with spina bifida eventually need shunts for hydrocephalus, only half of those who get the fetal surgery do, perhaps because, by repairing the spinal lesion, fluid does not build up as much in the brain.

The Vanderbilt team was so eager -- many say over-eager -- to spread the word, it put its findings on the Internet in mid-1997 and later helped publicize them in the magazine Woman's Day and on Dateline NBC. The study results were then submitted to the New England Journal of Medicine, but the journal declined to publish them. (The data remain unpublished, but have been submitted to another journal.)

Dr. Michael Greene , director of maternal and fetal medicine at Massachusetts General Hospital and the editor who reviewed the paper, says Bruner's paper was rejected because it dealt only with the first 10 or so successful cases and made no mention of subsequent ones, where the operation ``went sour.''

Bruner's enthusiastic self-promotion also irked his rivals, especially Adzick of Philadelphia, who notes that his team has performed about half of the 250 to 300 open fetal surgeries done worldwide and whose own work on one case was published in Lancet, a British medical journal. (Both men say they've now patched things up and refer patients to each other.)

And while, understandably, some parents of children with spina bifida complain on Vanderbilt's website that the surgery was not available to help them, those who have had it are immensely grateful.

Patricia Switzer, 34, a computer scientist, and her husband, Michael, 35, an Army test pilot stationed at Fort Rucker, Ala., discovered when she was 21 weeks pregnant that their fetus had spina bifida. She had the surgery three weeks later.

Though they're still fighting with their insurer to pay for the procedure -- and the $300-a-day drugs she needs to prevent premature delivery -- the Switzers are glad they took the risks. ``I would do anything for my baby,'' Patricia says.

As for the Stovers, their insurer did not cover the surgery, but their church raised $11,000 for them, and they'd do it all again if they had to.

``We aren't striving for a perfect baby,'' Dennis Stover says. ``We just want to do what's best. . .I feel we are pioneers, but someone has to be. Someone has to say, `I am willing to do this not just for my baby, but for the rest of babies.'

Judy Foreman is a member of the Globe staff. Her e-mail address is: foreman(AT SIGN SYMBOL)globe.com.

Previous ``Health Sense'' columns are available through the Globe Online searchable archives at http://www.boston.com. Use the keyword columnists and then click on Judy Foreman's name.

SIDEBAR:

'Closed' procedures are the future

At New England Medical Center, Wendy Andrasy, 33, a Weymouth police officer, has already reaped the benefits of this approach.

When she was pregnant two and a half years ago, her fetus had an enlarged bladder, a sign that something was obstructing the flow of fetal urine into the amniotic fluid. This can cause kidney damage as urine backs up; it can also sabotage lung development.

Fetal urine contains a growth factor that is ``essential for lung development,'' says Dr. Diana Bianchi, chief of genetics at the Floating Hospital for Children at New England Medical Center. Normally, the fetus ``is inhaling its urine and that is allowing this growth factor to get to the lungs.''

But Andrasy's fetus wasn't getting that growth factor. So when she was 20 weeks pregnant, Dr. Sabrina Craigo, a perinatologist at NEMC, slipped a tube through Andrasy's uterus, using ultrasound guidance, and placed a drainage shunt with one end in the fetal bladder and the other in the amniotic sac.

At the University of California in San Francisco, Dr. Michael Harrison, director of the fetal treatment center and the undisputed leader in fetal surgery, is pushing the envelope even further.

Harrison notes that 1 in 2,000 babies is born with a diaphragmatic hernia, a hole in the diaphragm that allows the intestines and sometimes the liver to poke up into the chest cavity. When this happens, the lungs get so compressed they never develop, which means that as soon as the baby is born, it dies.

The solution is counterintuitive: occlude the fetal windpipe. Fetal lungs make fluid that pours into the airway and out of the mouth; by blocking this outflow, the fluid, which spurs lung growth, is pumped back into the lungs.

Harrison's team has perfected a way to close the fetal windpipe endoscopically with a clip that is placed on the fetal trachea during surgery and left there for the remainder of the pregnancy. It is then removed during delivery by C-section so the baby can breathe normally. The results on the first dozen patients, not yet published, suggest that it works much of the time, he says. At Children's Hospital in Boston, Dr. Rusty Jennings , director of fetal diagnosis and treatment, is gearing up to do the trachea procedure, as well surgery for spina bifida and other problems.

At a number of hospitals nationwide, including New England Medical Center and Hasbro Children's Hospital in Providence, doctors are working on ways to use endoscopes and lasers to treat yet another fetal abnormality, the mixing of blood between identical twins whose blood vessels join in the placenta. When this happens, says Dr. Francois Luks, associate professor of surgery and pediatrics at Brown University, one twin's heart tries to pump blood for both, causing heart failure; the other twin often dies from anemia because it gets too little blood.

As for Andrasy, her son was born two years ago. The surgery prevented the child's death from underdeveloped lungs, but was not able to prevent kidney damage -- in fact, he needs a kidney transplant. But Andrasy, now pregnant again, was thrilled: ``He's wonderful. They saved his life. He's funny. He's a great kid. He smiles all the time.''