diagnosed with a rare genetic condition which means they will "probably never walk". The singer gave birth to Ocean Jade and Story Monroe Nelson-Foster prematurely last May with musician Zion Foster. On Sunday, Nelson said in an Instagram video that the girls have Spinal Muscular Atrophy (SMA), which she described as the "most severe muscular disease". "It does affect every muscle in the body, down to legs, arms, breathing, swallowing," she said.

In the video, she explained that her daughters had not been showing as much movement in their legs as they should be, and were struggling to feed properly. "After the most gruelling three, four months, and endless appointments, the girls have now been diagnosed with a severe muscular disease called SMA type 1," she said. "Essentially, what it does is, over time, it kills the muscles to the body, and if it's not treated in time, your baby's life expectancy will not make it past the age of two."

Nelson said that the girls were assessed at Great Ormond Street Hospital in London. There, she said, she was told that her daughters were "probably never going to be able to walk. They probably will never regain their neck strength, so they will be disabled". She added that they have since had treatment, which she was "so grateful for". "Because if they don't have it, they will die." Nelson said that she had to act as a nurse and put her daughter on "breathing machines" since the diagnosis. "The reason I wanted to make this video was because the last three months have honestly been the most heartbreaking time of my life. I literally feel like my whole life has done a 360."

But she said she believed that her daughters would "defy all the odds" and that with the right help, "they will fight this". She added that she wanted to share the diagnosis to help other children to get diagnosed as fast as possible. After resharing Nelson's story, partner Foster posted a smiling image of the twins with the caption: "Still smiling through all the challenges. Daddy loves you so much."  Nelson, 34, gave birth to her twins prematurely at 31 weeks, having previously revealed she had experienced rare complications during the pregnancy. (BBC/Instagram)