In which trimester is folic acid most crucial for preventing neural tube defects?

Folic acid is most crucial for preventing neural tube defects during the first trimester of pregnancy. This period is critical because the neural tube, which eventually develops into the baby's brain and spinal cord, closes within the first few weeks after conception—often before many women even realize they are pregnant. Adequate folic acid intake during this time helps ensure proper development of the neural tube and significantly lowers the risk of defects like spina bifida and anencephaly.

While folic acid remains important throughout pregnancy, particularly for overall fetal development and preventing anemia, its specific role in neural tube closure underscores the importance of starting supplementation before pregnancy and during the earliest weeks of gestation. This information highlights the vital need for women of childbearing age to ensure adequate folic acid intake in their diet or through supplements, especially in the first trimester when the risk of these defects is highest.