Neural tube defects
Defects of the neural tube are the most common birth defects; one in 1,000 live births in the United States are affected. Adding folic acid to women's diets reduces neural tube defects by 50-70% (Dukes Centre of human genetics).
Various neural tube defects are caused when different regions of the neural tube fail to close:
- Failure of the posterior region to close at day 27: Spina Bifida
- Failure of the anterior region to close: Anencephaly
- Failure of entire neural tube to close along entire body axis: Craniorachischisis
Spina bifida leaves some of the spinal cord exposed, the severity of the condition depends on how much of the spinal cord remains exposed. Anencephaly on the other hand leaves the forebrain exposed to amniotic fluid causing it to degenerate - interrupting fetal brain development and preventing the skull form forming. Anencephaly is fatal.