Low level of what during pregnancy can cause neural tube defects?

Low levels of folic acid (vitamin B9) during pregnancy can lead to neural tube defects in the developing fetus. Folic acid is crucial for proper neural tube formation, which develops into the brain and spinal cord. Insufficient amounts can result in conditions such as spina bifida and anencephaly. Therefore, it is recommended that women of childbearing age take folic acid supplements before and during early pregnancy.