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