Spina Bifida is usually an isolated birth defect. Although scientists believe that genetic and environmental factors may act together to cause this and other NTDs, 95 percent of babies with Spina Bifida and other NTDs are born to parents with no family history of these disorders. While Spina Bifida appears to run in certain families, it doesn’t follow any particular law of inheritance. If one child has Spina Bifida, the risk of recurrence in any subsequent pregnancy is about one in 40. If there are two affected children, the risk in any subsequent pregnancy is about one in 20. Spina Bifida also can occur as part of a syndrome with other birth defects. Here, inheritance patterns may differ from those of isolated Spina Bifida.