When a UK mum-to-be went in for her routine 20 week scan she had no idea that a month later her unborn child would be removed from her womb for surgery, then safely put back.

Bethan Simpson, 20, had been enjoying a smooth pregnancy until her doctor noticed that her unborn daughter’s head wasn’t measuring quite right during a 20 week scan.

“Fast forward 48hrs we were up in London having scans on her head and spine,” she wrote in an emotional Facebook post.

“We were told our little girl had spina bifida for sure.”

Spina bifida is a condition that impacts the development of a baby’s spine during the early stages of pregnancy, leaving a gap in the spine that can have serious health implications after the child is born.

It can cause leg weakness and difficulty moving, lack of sensation, poor bladder and bowel control and in some cases even learning difficulties, which often require multiple surgeries and ongoing care to manage.

The shocking news was delivered with few options for Simpson and her husband Kieron.

They could continue the pregnancy knowing their child would be affected by the condition, terminate the pregnancy while still in the early stages, or consider a new foetal surgery that could attempt to correct their daughter’s spine before she was born.

“We had to do it,” Simpson wrote.

She is only the fourth woman to ever undergo the surgery in the UK, which would see her daughter removed from her womb, operated on, then returned to her belly to continue pregnancy.

Simpson went in for surgery at the beginning of January. (Facebook)

On 8 January she went under at the University College London Hospital in the expert hands of Great Ormond Street Hospital doctors who repaired Simpson’s daughter’s spine, giving her a far better chance of a “normal life” than traditional postnatal surgery could.

Though risky, the surgery was a success and Simpson’s daughter “smashed surgery like you wouldn’t believe.”

Since the surgery Simpson has seen her daughter’s condition improve tremendously as the pregnancy progresses, writing that her little girl’s head has returned to a “normal shape and size” and she is growing well.

“Hopefully this surgery is going to allow our daughter to have the best chance at a 'normal life',” Simpson wrote.

“Our daughter has shown just how much she deserves this life.”

Simpson's scar from the breakthrough surgery. (Facebook)

There are still concerns, as the full impact of the baby’s spina bifida won’t be clear until she is born, but for the time being Simpson is just focused on letting her little girl grow.

She also hopes that her story can prove to other expecting parents that conditions like spina bifida are “not a death sentence.”

“Sadly 80% of babies in England are terminated when their parents get told their baby has this condition,” Simpson wrote.

“[My daughter] has the same potential as every one of us. Yes, there are risks of things going wrong but please think more about spina bifida. It's not what it used to be.”

Simpson said her pregnancy is progressing well since the surgery. (Facebook)

Currently the causes of spina bifida aren’t fully understood, with a combination of genetic, environmental and nutritional factors seeming to influence babies that develop the condition during early pregnancy.

It is one of the most common birth defects in developed nations, with around 150 children born with the condition in Australia each year, but an increased intake of folate in pregnant women during the first three months of pregnancy can help prevent the condition.