Deficiencies can lead to defects like spina bifida, where part of the spine grows outside the body, and anencephaly, a fatal condition in which much of the brain fails to develop.

• 对叶酸的缺乏会导致如脊柱破裂的缺陷，部分脊椎会生长在体外，还有无脑畸形，是指大部分的大脑没有发育成形这样一个严重的状况。