The 34-year-old singer has also vowed to campaign for babies to be screened for the condition at birth.
“I also wanted to let you guys know, I am starting a petition to try and get the newborn screening heel prick testing from birth and I just need you to know that I am so determined to make this happen and I am going to fight as much as I can to make this part of the newborn screening,” she said.
“It’s currently under review so I will keep you updated and also I will be on This Morning tomorrow talking about my baby girls. I love you all so much and I can’t thank you enough for the support. We have along way to go but I love you so much.”
At the weekend, Nelson said her daughters will “never walk” and have lost the ability to hold up their heads as a result of the condition.
“The girls have now been diagnosed with a severe muscle disease called SMA type one. For those of you who don’t know what SMA type one is, it’s a severe muscular disease that a baby can get.
“It’s done for spinal muscular atrophy, which can affect, well it does affect every muscle in the body, down to legs, arms, breathing, swallowing,” she said.
“And essentially, what it does is, over time, it kills the muscle to the body, and if it’s not treated in time, your baby’s life expectancy will not make it past the age of 2.
“When they assessed the girls at Great Ormond Street, we were told that they will never be able to walk and never regain their neck strength, so they will be disabled.”
Nelson said the babies have started having treatment and claimed they would have died without it.
“And so the best thing we can do right now is to get the treatment, and then just hope for the best. So hopefully the girls have had their treatment, which you’re so grateful for.
“Because if they don’t have it, they will die.”