Spina bifida is a birth defect that affects not only people but also dogs and cats. During gestation, the vertebrae typically grow around the spinal cord. When they fail to complete this developmental step, the spinal cord is left exposed at birth. iBoth genetic and environmental factors (toxins, nutritional deficiencies during pregnancy) can produce spina bifida. The condition is thought to be inherited, but the mode of inheritance has not been identified. Most often, spina bifida occurs in the lower back region (caudal lumbar spine).