International retrospective cohort study of neural tube defects in relation to folic acid recommendations

This retrospective cohort study was planned to determine whether recommendations to take folic acid have in fact lessened the risk of neural tube defects. Recommendations typically include eating a healthy diet and takingfolic acid supplements when planning pregnancy or throughout the childbearing years. In a few countries, including the United States, flour is fortified so that much of the population will receive at least a small supplemental amount of folic acid. Many governments promote the use of supplements because folic acid is inexpensive, safe, and easy to use. The authors acquired information on more than 13 million births from 13 birth defects registries in Norway that monitored rates of neural tube defects from 1988 to 1998. Cases of anencephaly and spina bifida totaled 8636. Rates of defects were stable during the 10-year monitoring interval in most areas. There were no evident changes in rates of defects after local recommendations were issued. Comparable findings were obtained when analyzing anencephaly and spina bifida separately and combined. Folic acid use in Europe is, in general, low; in Norway, it is approximately 10%. In China, intensive educational efforts and a high rate of planned pregnancies probably are responsible for the effectiveness of a public health campaign to promote the use of folic acid supplements. Rates of folic acid use generally follow economic and educational trends. Fortifying flour with folic acid holds promise for delivering some folic acid to a large part of the population, crossing social and economic barriers. Blood folate levels have increased rapidly where this practice is followed. It is estimated that thousands of neural tube defects occurring since 1992 could have been prevented.