Ellis takes pictures of her baby on her phone. She said with certainty that he was perfect. The journey to his arrival has been more difficult than most others. Austin has spina bifida and is one of a growing number of babies in the UK to have undergone a revolutionary foetal surgery.

The Guardian was given access to observe the same procedure on another mother and baby from inside the operating theatre that surgeons at King's College Hospital did for Austin. The procedure may be the difference between Austin walking or not.

It is a landmark step in managing patients with spina bifida and improving outcomes and quality of life.

There is a hole in the back and the spine does not close completely. Parents had to wait until a baby was born to have corrective surgery. The risks of hydrocephalus, where too much fluid builds up in the brain, can be reduced if the baby is operated on during the second trimester.

Emily and her husband, Simon, were diagnosed with spina bifida after their baby's spine was not forming correctly. It was the hardest thing to find out. It feels like you're grieving.

The couple decided to go ahead and have foetal surgery in order to give their baby the best chance of survival. King's is the only centre in the UK that offers the procedure at 27 weeks pregnant.

Emily and Austin Ellis at King's College hospital in London

Emily and Austin Ellis at King's College hospital in London. Photograph: David Levene/The Guardian

The Guardian observed another mother and baby going through a procedure that is not for the faint-hearted two floors down from the Nicu, where Austin just had his first bottle-feeding.

At least a dozen other specialists, including an anaesthesiologists and scrub nurses, will crowd into the theatre to watch the operation. A pregnant patient is hidden beneath surgical sheets.

The uterus, a glossy sphere, is lifted out of the body. Three small surgical ports are made by the surgeons. Theamniotic fluid is drained and the uterus is inflated with carbon dioxide gas to stop the baby from floating.

As the camera enters the port, it illuminates the uterus from inside like a red globe with vessels. Three large screens will be used to help guide the surgery. There is a big bubble on the baby's back.

A pair of surgical tools are threaded through the two ports and Zebian begins by cutting away the blisters that are attached to the spine. He uses two pivot points to cut it away. Santorum-Perez stitches a protective biocellulose patch over the severed spine and a second patch to encourage skin regrowth.

Parents feel they would do anything to improve their outcome

Since the first procedure four years ago, their technique has evolved, and the mother is the 22nd patient to receive the surgery at King's. The hybrid approach seems to reduce the chance of premature delivery.

Prof Kypros Nicolaides, the director of the Harris Birthright Centre and consultant in foetal medicine at King's, believes that society has become more supportive of people with disabilities and that this has led to a stronger desire to push the boundaries. He said parents would do anything to improve their result. Mobility is likely to improve for most children with spina bifida.

After four hours on the operating table, the uterus is filled withamniotic fluid and sealed. The pregnant woman will be allowed to return to her home in a few days.

Austin is breathing by himself, taking feeds from a bottle and kicking his legs, which is a crucial sign of mobility. The family hopes to take their new baby home soon, even though Harry is yet to meet him. Emily says that she and her husband are taking every day as it comes.