[Folic acid dose in the prevention of congenital defects]

Med Clin (Barc). 2007 Apr 28;128(16):609-16. doi: 10.1157/13101744.
[Article in Spanish]


Background and objective: Synthetic folic acid (FA) is in the form of pteroylmonoglutamate (PGA), a form that does not occur in nature, where it is in form of pteroylpolyglutamate, mainly as 5-methyltetrahydrofolate. The organism transforms PGA into 5-methyltetrahydrofolate, and it has been detected that this process is saturated at doses of 0.4 mg of PGA. Recently, some concern has been expressed on the use of higher than recommended doses of FA, because of the possibility of saturating the biotransformation process and the consequent plasmatic accumulation of unmetabolized synthetic FA. The objective of this study is to analyze the doses of synthetic FA that are being currently used in Spain, as well as its secular and geographic distribution.

Patients and methods: The study was based on 16,761 mothers of non-malformed infants from the data base of the Spanish Collaborative Study of Congenital Malformations. All forms of folates (folic or folinic) have been considered under the general term of FA.

Results: Although an increasing trend in the proportion of mothers using FA in the last study period (2003-2004), only 17.37% of the mothers had FA supplements since before pregnancy. Among the rest, 71.13% started using FA once they knew they were pregnant, and 11.50% never took this vitamin. In addition, more than 70% of mothers who took FA ingested doses of 4 mg or more. The results by Spanish Autonomic Regions are quite similar, with more that 50% of the mothers (of the period 2003-2004), in the great majority of the Regions, taking mean daily doses of FA that are between 12.5 and 20-fold higher than the recommended 0.4 mg/day.

Conclusions: Most of women are having FA after conception, or do not ingest FA at all. Most of those women who take FA use doses much higher than recommended. The results of this study show that it is necessary to spread these aspects among the health professionals implicated.

Publication types

  • English Abstract
  • Multicenter Study

MeSH terms

  • Congenital Abnormalities / epidemiology
  • Congenital Abnormalities / prevention & control*
  • Female
  • Folic Acid / administration & dosage*
  • Humans
  • Pregnancy
  • Spain


  • Folic Acid