Wald N J
Department of Environmental and Preventive Medicine, Wolfson Institute of Preventive Medicine, St. Bartholomew's Hospital Medical College, London, UK.
Ciba Found Symp. 1994;181:192-208; discussion 208-11. doi: 10.1002/9780470514559.ch12.
The results of the MRC Vitamin Study have established the specific role of folic acid in the prevention of neural tube defects. Folic acid supplementation (4 mg/day) at the time of conception reduced the recurrence rate by about 70%. Evidence from observational studies and the Hungarian randomized trial (that used 0.4-0.8 mg/day supplemental folic acid) indicates that a similar level of prevention can be achieved among women who have not already had an affected pregnancy and that this may be achieved with a lower dose of folic acid. The medical implications of these results are important. (1) Women planning a pregnancy should take folic acid supplements. (2) Because a large proportion of pregnancies are unplanned and many of those that are planned will occur in women who will not have taken folic acid supplements, a complementary general public health strategy is needed, based on dietary advice and food fortification designed to achieve the benefit with adequate safety. (3) Any public health prevention strategy needs to be monitored for efficacy and possible harm. (4) Research is needed on the dose-response relationship between folic acid and neural tube defect prevention and the mechanism of action.
医学研究委员会维生素研究的结果已证实叶酸在预防神经管缺陷方面的具体作用。怀孕时补充叶酸（4毫克/天）可使复发率降低约70%。观察性研究和匈牙利随机试验（使用0.4 - 0.8毫克/天的补充叶酸）的证据表明，在尚未有过受影响妊娠的女性中可实现类似程度的预防效果，而且较低剂量的叶酸可能就可以做到。这些结果的医学意义重大。（1）计划怀孕的女性应服用叶酸补充剂。（2）由于很大一部分怀孕是意外怀孕，而且许多计划怀孕的女性不会服用叶酸补充剂，因此需要一项基于饮食建议和食品强化的补充性公共卫生战略，以在确保足够安全的前提下实现益处。（3）任何公共卫生预防战略都需要监测其效果和可能的危害。（4）需要开展关于叶酸与神经管缺陷预防之间的剂量反应关系以及作用机制的研究。
