A small number of women who do not test positive as carriers for Duchenne may still be able to pass a faulty DMD gene to their children. This situation is called germline mosaicism and is caused by a mutation in the DMD gene in the cells of some of the mother’s eggs. The mutation is not seen in the DMD gene in the rest of the mother’s cells. If one of the affected eggs is fertilized, the resulting child will have DMD if a boy or be a female carrier if a girl. It is estimated that around 15% of mothers of boys with Duchenne, who do not appear to be carriers, could pass a faulty DMD gene to their children in this way.