Dolin Cara D, Deierlein Andrea L, Evans Mark I
Department of Obstetrics and Gynecology, New York University Langone Health, New York, New York, USA.
College of Global Public Health, New York University, New York, New York, USA.
Fetal Diagn Ther. 2018;44(3):161-165. doi: 10.1159/000491786. Epub 2018 Aug 22.
Some medical practices have been ingrained in custom for decades, long after "proof" that they were effective was established. It is necessary to periodically reevaluate these practices, as newer theories and research may challenge the evidence upon which they were based. An example is the decades' old practice of recommending a 4-mg (4,000-µg) supplement of folic acid to women who are at risk for recurrent neural tube defect (NTD) during pregnancy. This recommendation was based on findings from a randomized clinical trial in 1991. Since then, multiple studies have confirmed the utility of 400-800 µg of folic acid in lowering both primary and recurrent risks of NTDs, but no studies have established any further reduction in risk with doses over 1 mg. Current understanding of folic acid metabolism during pregnancy suggests that at higher doses, above ∼1 mg, there is not increased absorption. Recent evidence suggests that 4 mg folic acid supplementation may not be any more effective than lower doses for the prevention of recurrent NTDs. Thus, we recommend that it is time for clinicians to reexamine their reliance on this outdated recommendation and consider using current recommendations of 400-800 µg per day for all patients in conjunction with assessment of maternal folate status.
一些医疗实践已经在习俗中根深蒂固了几十年，远在其有效性的“证据”确立之后。定期重新评估这些实践是必要的，因为更新的理论和研究可能会挑战它们所基于的证据。一个例子是几十年来一直向孕期有复发性神经管缺陷（NTD）风险的女性推荐4毫克（4000微克）叶酸补充剂的做法。这一推荐基于1991年一项随机临床试验的结果。从那时起，多项研究证实了400 - 800微克叶酸在降低NTD的初次和复发风险方面的效用，但没有研究表明剂量超过1毫克能进一步降低风险。目前对孕期叶酸代谢的理解表明，在高于约1毫克的较高剂量下，吸收不会增加。最近的证据表明，补充4毫克叶酸预防复发性NTDs可能并不比低剂量更有效。因此，我们建议临床医生是时候重新审视他们对这一过时推荐的依赖，并考虑对所有患者采用目前每天400 - 800微克的推荐剂量，同时评估孕妇的叶酸状态。
