In some cases, a child is the first person in his family to be diagnosed with DMD. This can happen if the change in the DMD gene happened by mistake during the making of the egg or sperm. When this happens it is called a new or de novo mutation. In this case, the risk that the mother would have another child with DMD is low. However, sometimes, the boy's mother is a carrier of DMD, but is the first person in her family with the change in the DMD gene. This means the change in the DMD gene happened by mistake during the making of the egg or the sperm that came together to form the fertilized egg that developed into her. In this case, the mother is a carrier and would have a 50% risk that each son will have DMD and also a 50% risk that each daughter will be a carrier. To complicate the inheritance even more, a woman may not have the change in the DMD gene in all of her cells. She may only have the change in the gene in some of the cells of her body, including her eggs, or even just in some of her eggs. This can happen if the mistake happens after the egg is fertilized, but sometime early in development of the fetus. In these cases the risk of passing the changed gene to her children depends on how many of her eggs are affected