What is spinal muscular atrophy? As Jesy Nelson announces her twin daughters have condition, how common is it?

The 34-year-old singer shared a video on her Instagram page earlier today (Sunday January 4), in which she revealed her baby girls, Ocean Jade and Story Monroe Nelson-Foster, have the rare genetic condition.

In a video where she spoke directly to the camera and became emotional several times, Jesy said that doctors had warned her that the little girls, who are now seven-months-old, will never walk.

“Once the girls got treated it was a very rapid process. Time is of the essence with this disease. When they assessed the girls at Great Ormond Street, we were told they were never going to be able to walk. They would probably never regain their neck strength. They will be disabled," she said.

"The best thing we can do right now is to get them treatment and hope for the best. Thankfully the girls have had their treatment which I’m so grateful for. If they didn’t have it they would die."

She added that she now feels like she has become a “nurse” for her children and has “had to do stuff no mother should have to do to their child”.

The mum-of-two went on to describe this was “the most heartbreaking time of my life." But, she cried as she continued to say she is thankful her daughters are alive: "I know I have to be grateful. At the end of the day they are still here and that's the main thing. They've had their treatment.

What is spinal muscular atrophy?

Spinal muscular atrophy (SMA) is a serious genetic condition that gets worse over time. Usually, the life-limiting condition is passed on if both parents are born with a faulty gene. Although they may not have SMA themselves - they are known as carriers.

According to the NHS, typical symptoms include floppy or weak arms and legs, shaking muscles, and swallowing and breathing difficulties. The illness currently has no cure but medics are investigating new treatments.

Until 2019, there were no treatment options available for children with SMA, which is the leading genetic cause of death in children. However, babies could potentially have the ability to sit, crawl and walk after being treated with the new treatment.

There are different types of SMA: type 1, type 2, type 3 and type 4. Babies with type 1 rarely survived beyond the first few years of life, the NHS says. In recent years, outcomes have improved with early diagnosis and treatment.

Most children with type 2 survive into adulthood and can live long lives. Whereas types 3 and 4 do not usually affect life expectancy.

Although the illness affects patients physically, there has been no evidence to suggest it has an impact on their cognitive function.

How common is spinal muscular atrophy?

Around 70 children are born with spinal muscular atrophy (SMA) each year in the UK, according to the NHS. While rare, it's one of the most common severe hereditary diseases affecting infants and children.

What treatment is available for spinal muscular atrophy?

Five years ago, a groundbreaking treatment for SMA was introduced in the UK, a US gene therapy Zolgensma, which has been called the most expensive drug in the world.

Zolgensma, which has a list price of £1.79 million per dose, was made available on the NHS after the health service struck a deal with manufacturers Novartis Gene Therapies in March 2021.

The drug contains a healthy copy of a missing or faulty gene called SMN1, the BBC reports. The gene is then put inside a non harmful virus to make a replacement gene.

The virus is needed in the body to deliver the replacement gene into the nucleus of motor neuron cells. Then healthy cells start producing missing SMN protein - needed for muscle movement.

Arthur Morgan, then aged just five months, was the first child in the UK to be given the treatment back in May 2025. He had only been diagnosed with SMA three weeks earlier. Arthur is now four-years-old and living in Biggin Hill, London, with his parents Reece and Rosie.

In April 2025, family friend Lewis James raised almost £4,000 for the youngster and his on-going medical care by running the London Marathon.

Research is continuing into possible new treatments for SMA.