Final answer:
Anencephaly is a neural tube defect characterized by elevated levels of AFP in utero, resulting in a partial or complete absence of brain tissue in the baby.
Step-by-step explanation:
Anencephaly is the condition characterized by elevated levels of AFP in utero. It is a more severe neural tube defect where there is a partial or complete absence of brain tissue in the baby. This occurs when the neural tube, which develops into the brain and spinal cord, fails to close properly during early pregnancy.