how many babies born in us with spinal muscular atrophy
Hereâs what you need to know about spinal muscular atrophy (SMA): 1  SMA is the number one genetic cause of infant mortality. 2  About 10 to 16 out of every 100,000 children are born with SMA. SMA is the number one genetic cause of infant mortality. 2  About 10 to 16 out of every 100,000 children are born with SMA. 3  There are three types of SMA that vary greatly by age at onset and severity. 4  SMA type is determined by the highest motor function the child achieves.