What causes Hirschsprung's disease?

Hirschsprung's disease develops before a child is born. Normally, nerve cells grow in the baby's intestine soon after the baby begins to grow in the womb. These nerve cells grow down from the top of the intestine all the way to the anus. With Hirschsprung's disease, the nerve cells stop growing before they reach the end.

No one knows why the nerve cells stop growing. But we do know that it's not the mother's fault. Hirschsprung's disease isn't caused by anything the mother did while she was pregnant.

Some children with Hirschsprung's disease have other health problems, such as Down's syndrome and other rare disorders.

source: http://digestive.niddk.nih.gov/ddiseases/pubs/hirschsprungs_ez/index.htm