My son was stillborn and had twelve fingers, twelve toes. what are the chances i will have another child with this?

Hard to say: Were there other issues ? This can arise as a single defect, not associated with other problems and not the cause of the stillbirth. This can be a new autosomal dominant feature or passed through the family, it can skip a generation. This can also occur as part of a syndrome or collection of associated problems. A geneticist can usually help you sort through this issue.