Reason for withdrawal from publication
This review has been withdrawn from publication because it has been updated by a new review: De-Regil LM, Fernández-Gaxiola AC, Dowswell T, Peña-Rosas JP. Effects and safety of periconceptional folate supplementation for preventing birth defects. Cochrane Database of Systematic Reviews 2010, Issue 10. Art. No.: CD007950. DOI: 10.1002/14651858.CD007950.pub2.