Evidence suggests that folic acid may help prevent the development of spina bifida, a common disabling birth defect. It is recommended that women increase their folic acid intake during pregnancy, especially in the first three months. Why is the timing of the folic acid intake relevant?

• A. Substances can most easily enter the embryo through the placenta early in pregnancy.
• B. The embryo has not yet been implanted in the wall of the uterus.
• C. The mother's hormone levels are highest.
• D. The cells of the embryo are not yet fully activated.
• E. The most drastic and rapid changes, including neural tube formation, are occurring in the embryo.

Answer: (E)

Verified step by step guidance

1. Understand the role of folic acid: Folic acid is crucial for the proper development of the neural tube, which later becomes the brain and spinal cord of the embryo.
2. Identify the critical period for neural tube development: The neural tube forms very early in pregnancy, typically within the first 28 days after conception, often before a woman knows she is pregnant.
3. Recognize the importance of timing: Since the neural tube forms so early, it is essential for women to have adequate folic acid levels before and during the early stages of pregnancy to prevent defects like spina bifida.
4. Consider the biological processes: During the first trimester, the embryo undergoes rapid cell division and differentiation, making it a sensitive period for development and the prevention of birth defects.
5. Conclude with the relevance of early folic acid intake: The timing is crucial because the most drastic and rapid changes, including neural tube formation, occur in the embryo during the first trimester, necessitating sufficient folic acid intake to support these processes.