In humans, spina bifida is a split in the vertebral column (the spine). It is a birth defect. During early pregnancy, the spine closes around the membranes in the spinal chord. This happens between the 22nd and the 28th day of pregnancy. With spina bifida, this doesn't fuilly happen. In Western Europe, spina bifida happens in about 1 in 1000 births; girls are affected slightly more often than boys.
It needs to be treated within the first few days after birth. Usually, the people affected are severely disabled. Taking folate before and during the pregnancy can reduce the risk of this birth defect.