The complicated two-hour operation was carried out on a five-month-old foetus at the Necker hospital in Paris.
Details of the procedure, which was carried out earlier in the summer, have only just been revealed after the birth of the baby through a caesarean ten days ago
Following the operation, doctors saw a "normalisation of the brain abnormalities" in the foetus, with the hospital saying both mother and baby were in fine health.
“Ten days after the surgery, the brain anomalies [in the foetus] that were caused by the disorder had disappeared,” Dr Jean-Marie Jouannic, who led the procedure, told the AFP news agency. “It’s incredible to be able to protect this little girl’s brain to enable future learning.”
If left untreated, the spina bifida can lead to partial or total paralysis of the lower limbs as well as a build up of fluid inside the brain.
After discovering the foetus had the defect, a disabling congenital disorder which leaves a gap in the spine, doctors offered the mother the option of the operation, which comes with a risk of causing a premature birth.
The surgery involves cutting through the mother’s abdomen, her womb and the amniotic sac surrounding the baby. The baby has to be kept face down in the fluid to ensure it doesn’t start to breathe on its own.
There was the added concern that the surgery had never before been carried out in France, with only around a dozen hospitals offering it worldwide.
“In France we have been considering this surgery for around ten years. Many were asking whether there was a place for this type of intervention in our country,” Jouannic told Le Parisien newspaper.
“In reality the pre-natal methods of diagnosis in France are among the best in the world. The majority of couples choose to terminate their pregnancy when they find out [that there is a problem of this nature],” he added.
“Today there is a demand from couples who want to undergo this surgery. It would almost be unethical not to offer it to them.”
Dr Jouannic points out that the baby will not be cured of the birth defect but the consequences of it will be reduced as a result of the surgery.
The mother and baby are expected to leave hospital in the next few days.