Folic acid for the prevention of congenital anomalies

Paediatricians need to be aware of the broad implications that sufficient maternal folic acid intake has on the wellbeing of the embryo and fetus. There is now strong evidence that adequate periconceptional maternal folic acid supplementation during critical periods of organ formation is associated with reduction in both the occurrence and recurrence of neural tube defects, congenital heart defects (particularly conotruncal heart defects), obstructive urinary tract anomalies, limb deficiencies, orofacial clefts and congenital hypertrophic pyloric stenosis. Inadequate maternal folic acid intake is associated with preterm deliveries, intra-uterine growth retardation, placental abruption and infarction, while maternal folic acid supplementation is associated with a reduction in preterm deliveries and intra-uterine growth retardation. Recently adequate folic acid intake in adults has been associated with a reduction in adult cardiovascular disease and some cancers. A common mutation in the 5,10 methylenetetrahydrofolate reductase gene has been identified which produces a thermolabile variant of 5,10 methylenetetrahydrofolate reductase with reduced enzyme activity. The common mutation is a risk factor both for neural tube defects and adult cardiovascular diseases. Folic acid acts to increase the activity of the variant methylenetetrahydrofolate reductase thereby reducing plasma homocysteine levels. However the polymorphism does not explain all of the protective effects of folic acid.