The NHS Newborn Blood Spot Test, external, usually taken when babies are five days old, already checks for a number of rare but serious health conditions, with SMA now being included in participating areas as part of an NHS in-service evaluation.
The rare genetic condition affects the nerves that control muscles, causing progressive muscle weakness and affecting movement, breathing and swallowing.
It affects about one in 10,000 babies, external, including the twins of former Little Mix singer Jesy Nelson, who had previously campaigned for every baby to be tested.
Willis told BBC Radio Shropshire there were different types of SMA and some babies showed signs of muscle weakness from birth.
One of the most severe forms, SMA type 1, external develops within the first six months of life and, without treatment, can severely limit life expectancy.
“Some babies come out and they’re already showing signs of muscle weakness,” Willis explained.
“Most of the time these babies will start losing their motor milestones and muscle weakness is obvious to the parents within weeks of birth. They are often called floppy babies or lazy babies.”
Babies without treatment “don’t achieve sitting”, Willis explained, adding children are sometimes diagnosed after ending up in intensive care for chest infections.
“It is quite severe and it goes on to affect not just their ability to sit, stand, [or] walk, it affects their breathing muscles. So these children end up on ventilators,” she said.