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Objective  To systematically summarise the available evidence concerning the rate of folic acid supplement use pre- and periconceptionally, to identify those characteristics associated with low rates of use and to assess whether folic acid public awareness campaigns are associated with higher folic acid use.

Design  Systematic overview.

Setting  Survey studies.

Population  Women of reproductive age, most of whom were currently or recently pregnant.

Methods  Two investigators searched MEDLINE, Embase and Nutriotiongate databases between 1990 and 2003. Bibliographies of retrieved references were scanned for other relevant publications, and authors were contacted if necessary. Studies were included that evaluated the rate of folic acid supplement use either before conception or in early pregnancy.

Main outcome measures  Rate of preconceptional and/or periconceptional folic acid use, rate of planned pregnancy in each study, as well as significant characteristics differentiating non-users from users of folic acid, including the effect of folic acid awareness campaigns.

Results  A total of 52 studies were included. In 34 studies, reported preconceptional folic acid use varied from 0.9% to 50%. In 49 studies, the reported rate of periconceptional supplement use ranged from 0.5% to 52%. Significant predictors of reduced periconceptional folic acid use were a low level of formal education, immigrant status, young maternal age, lack of a partner and an unplanned pregnancy. Four studies examined the effect of mass media campaigns on periconceptional folic acid use; the reported rates increased significantly, by a factor of 1.7 to 7.2, but in no study was the post-campaign rate above 50%.

Conclusions  In many countries, fewer than 50% of women take periconceptional folic acid supplements. Consideration should be given to the practical advantages of folic acid fortification of centrally processed foods, such as wheat, corn and rice flour, while further promoting vitamin tablet supplement use and planned pregnancy.