"The last three months have been the most heartbreaking time of my life."

The former Little Mix singer gave birth to twin girls Ocean Jade and Story Monroe Nelson-Foster in May last year, with her musician fiancé Zion Foster.

However, the 34-year-old has now revealed that her twins have been diagnosed with Spinal Muscular Atrophy (SMA), and doctors have told her that her daughters will never walk.

Taking to Instagram, Jesy explained what the diagnosis means.

SMA affects every muscle in the body, and impacts everything from their legs to swallowing.

She says she is acting as a full-time nurse to her daughters, and is having to do 'things no mother should.'

"I wanted to come on here to share some news with you guys. I’m not actually sure where to start with this video," she began.

"A few months ago my mum noticed that the girls were not showing as much movement in their legs as they should be.

"It wasn’t really a concern to me at the time," she said.

"From the minute I left NICU I was told, 'Your babies are premature so don’t compare your babies to other babies. They won’t reach the same milestones just take them as they are.'

"It didn’t really ring alarm bells to me. They are my first set of children and I was told not to compare to them. Health care visitors insisted everything was fine and the girls were healthy.

"There were a few signs later on that the girls were struggling to feed properly. We would take them to the GP and say ‘Our babies are not feeding as frequently as they should.' They said it was fine and to try little and often."

She continued:  "Long story short, after the most gruelling three to four months and endless appointments, the girls have been diagnosed with a severe disease called SMA type one. It stands for Spinal Muscle Atrophy which affects every muscle in the body from legs, arms, swallowing.

"Over time it kills the muscles in the body. If it’s not treated in time, your babies life expectancy will not make it past the age of two.

"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," Jesy added.

"The best thing we can do right now is to get them treatment and hope for the best," she said.

"Thankfully the girls have had their treatment which I’m so grateful for. If they didn’t have it they would die."

Jesy went on to explain how her life has been impacted since the diagnosis.

"The hospital has become my second home. I feel like I've had to become a nurse within two weeks of getting the diagnosis. I've had to do stuff no mother should have to do to their child.

"I made this video because the last three months have been the most heartbreaking time of my life."

She concluded, breaking down in tears: "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.

"I truly believe that my girls will defy the all the orders and with the right help they will fight this."

During her pregnancy, Jesy shared that she had undergone complications, including her twins being diagnosed with twin-to-twin transfusion syndrome (TTTS).

The condition affects 10 to 15 per cent of identical twins who share a placenta, and “can have serious consequences”.

Jesy gave birth prematurely at 31 weeks after undergoing surgery to prevent complications related to TTTS.