Fetal surgery – or operating on babies while they’re still in their mother’s womb — is a relatively new field of medicine that’s evolved over the last 30 years.
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Advances in science and technology have opened the door to exciting possibilities for surgeons to do prenatal operations that can, in some cases, prevent the death of a fetus or improve the quality of life for babies with certain birth defects.
Among the most common birth defects is spina bifida, a condition where a baby’s spinal column doesn’t form properly. In its most severe form (myelomeningocele), spina bifida leaves part of the baby’s spinal cord and nerves exposed through an opening in the baby’s back.
Because of the nerve damage they sustain, most children with spina bifida cannot walk, and many have trouble controlling their bowel or bladder functions.
The baby’s spinal fluid can also leak out, causing a condition called hydrocephalus that can lead to brain damage, seizures or blindness.
Surgery can fix the abnormal opening once the baby is born, but it can’t undo any damage that’s already been done to the exposed nerves. Babies with spina bifida may also need to have additional surgery to have a plastic shunt inserted into their brain to drain off the excess fluid caused by hydrocephalus.
But performing the corrective surgery on babies while they’re still in the womb could reduce the damage by shielding the nerves and sealing in spinal fluid sooner, says Director of Fetal Surgery Darrell Cass, MD.
“This advancement is entirely driven by our ability to see inside the uterus with fetal imaging, which is based on ultrasound and MRI,” says Dr. Cass. “As our computer technologies get faster and better, the resolution of what we can see gets better. We can now see, with remarkable detail, the exact anatomy of the fetus.”
Spina bifida surgery in utero
The surgery involves opening up the mother’s abdomen and making a 2-inch incision in her uterus. Through that incision, a neurosurgeon can operate on the fetus’s spine.
Dr. Cass was previously part of one of the first teams to offer fetal surgery for spina bifida after results from a landmark clinical trial were released in March 2011.
Published in the New England Journal of Medicine, the trial shined light on the potential benefits of doing this surgery pre-birth: The babies who received the fetal surgery were twice as likely to be able to walk independently at age 3, and 50 percent fewer of them needed cerebrospinal-fluid shunts.
More recent data suggest that the benefits of fetal surgery may be even greater, Dr. Cass says.
But fetal spina bifida surgery is not without risk. The mother’s uterus could rupture, or she could go into pre-term labor if the uterus gets irritable and doesn’t heal well. There’s also a small risk that the baby could die, which has happened in a few cases, Dr. Cass says.
Because of those risks, the operation is only appropriate for a select group of mothers and babies.
The mother, for one, must be free of any major medical problems that could complicate the surgery. “The mom’s safety has to be our No. 1 priority,” Dr. Cass says.
The baby must have the type of complication that causes hydrocephalus, and must be at risk for a poor outcome if surgery isn’t performed until after birth.
The future of fetal surgery for spina bifida
The number of medical centers offering this challenging operation has increased but is still relatively low, and there is much yet to learn about the optimal candidates, timing and techniques for it, Dr. Cass says.
Remember that important clinical study that was published in 2011? While it was great in showing the benefits of surgery in utero, the study involved many tightly controlled variables (as a good scientific study does). For example, all of the operations were performed on mothers who were less than 27 weeks along, and none of them had BMIs over 35. So there isn’t necessarily published data on how the operation might go in heavier women, or women who are further along.
These variables need to be evaluated experimentally, Dr. Cass says.
There’s also room for further advancement in surgical technique. Dr. Cass is hopeful that medical centers will soon be able to offer the procedure less invasively using a fetoscopic or robotic technique. These approaches could potentially reduce the risk of uterine rupture, because they would require only a few tiny openings in the uterus rather than a 2-inch cut. It would also allow the mother to deliver vaginally, whereas mothers who have the open surgery or no surgery must have a cesarean section.
“The cool thing is, the medical centers that are doing fetal surgery are getting together as a consortium sponsored by the North American Fetal Therapy Network and putting their cases in a database,” he explains. “So we’re going to be able to do research on everyone’s data and answer some of these important questions.”