Spina bifida is customarily treated in the 24 to 48 hours immediately following childbirth: surgeons sew up the spinal cord and tuck it back into the baby's body, preventing the condition from degenerating any further.

Technology including genetic analysis, neuroimaging, and high-resolution foetal magnetic resonance imaging (MRI) are allowing doctors to peer into the nervous systems of developing foetuses and already diagnose them – earlier and more frequently – with any life-altering conditions they'll experience once born.

And the field is "right on the precipice" of a whole new dimension of therapies, says Jeffrey Russ, a pediatric neurologist at Duke University who recently wrote an academic essay describing in-utero treatment as the "next frontier" in neurology.

So, when doctors at The Ottawa Hospital in Ontario, Canada, ran tests on an unborn girl called Ayla Bashir in February 2021, revealing she had inherited the same genes that led two of her siblings, Zara and Sara, to be diagnosed with Pompe's after birth – they knew they had to act quickly.

So while surgeries and chemical therapies like those developed by Farmer and Mackenzie are mostly short-lived procedures, once doctors edit the genetic code of an unborn baby these changes, and their effects, will be forever.

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