My wife's father had muscular dystrophy what are her chances of passing it to our baby? Should we test?

Depends on type. More than 30 genes have been identified causing different types of md. 3 types of inheritance: x-linked recessive-mothers are carriers thus sons have 50% chance of developing md. Daughters have 50% chance of being a carrier. Autosomal recessive-both parents must carry & pass on md gene. Kids will have 25% chance of developing md. Autosomal dominant-each child of affected parent has 50% chance.