atrophySpinal Muscular Atrophy (SMA) is an autosomal recessive genetic disorder that causes progressive muscle wasting and weakness. It is the most common genetic cause of infant death, and the carrier frequency is about 1 in 50 in the general population. When both parents are carriers, there is a 1 in 4 chance the child will be affected. Screening for SMA is offered to all women who are considering pregnancy or are currently pregnant.