尤其在骨髓初期开始成长的时候，当然那时孕妇可能还不知道自己怀孕了，最安全的办法就是让她每天服用400微克的维生素b(叶酸的合成体)。

Since the spinal cord starts to develop extremely early-before a woman may know she's pregnant-the safest course is for her to take 400 micrograms of folic acid (the synthetic form of folate) daily.

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