Neural tube defects are a group of related birth defects in babies that involve the neural tube, which eventually grows into the baby’s brain and spinal cord. This type of defect forms extremely early in the pregnancy, often before the woman is aware that she is pregnant. Two common neural tube defects are spina bifida, which affects the spine, and anacephaly, which affects the brain. Neural tube defects usually occur because of a folate deficiency and are especially common in people with the MTHFR mutation. It is important for women with MTHFR to supplement the active form of folate if they are actively trying to get pregnant.