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Folic Acid and Prevention of Neural Tube Defects

Information Update from PHAC - 2008

The recent release of the Joint Society of Obstetricians and Gynaecologists of Canada - Motherisk Clinical Practice Guideline on Preconceptional Vitamin/Folic Acid Supplementation has generated questions about Public Health Agency of Canada and Health Canada recommendations on this topic. This update aims to clarify the Public Health Agency of Canada's recommendations on this important issue.

Women who take a vitamin supplement containing folic acid before conception and in early pregnancy have a reduced risk of the fetus being affected by a neural tube defect (NTD). In response to this scientific evidence, and recognizing that some pregnancies are unplanned, the federal government has taken steps to help women of childbearing age increase the amount of folic acid that they consume:

Vitamin supplementation

The Public Health Agency of Canada recommends that all women who could become pregnant take a daily multivitamin containing 0.4 mg of folic acid. We recommend that women talk to a health care provider, such as their doctor or pharmacist, to choose the supplement that is best for them.

Women who become pregnant should talk to their prenatal care provider about a supplement to meet their needs for additional nutrients (such as iron) during the pregnancy.

All women should eat a healthy, well-balanced diet according to Canada's Food Guide, that includes good sources of folic acid such as dark green vegetables, corn, dried peas, beans, lentils, oranges and orange juice.

Some women are at higher risk of having a NTD-affected pregnancy. These include women who have had a previous NTD-affected pregnancy and those with a near relative who has an NTD. Also, women with epilepsy, obesity or poorly-controlled diabetes are at increased risk. Women at higher risk of an NTD-affected pregnancy should talk to their doctor about steps they can take to prepare for a healthy pregnancy. They may need more than 0.4 mg of folic acid daily.

Women should not take more than 1 mg of folic acid daily unless they are under the advice and care of a physician. This will allow for evaluation of vitamin B12 status and assessment of other issues such as possible interaction with other medications.

Mandatory food fortification

Since 1998 the Government of Canada has required that folic acid be added to all white flour and enriched pasta and cornmeal products sold in Canada. Studies have shown that there has been a significant decline in the rates of NTDs in Canada since mandatory fortification began. For example, a 7-province study showed a reduction of 46% in the overall rate of NTDs, including live births, stillbirths and cases detected prenatally in pregnancies that were subsequently terminated.

Where are we now?

The decline in rates of NTDs in Canada is a tremendous public health success story. Food fortification is in place, and according to the Public Health Agency of Canada's 2006 Maternity Experiences Survey 58% of Canadian women took multivitamins containing folic acid in the three months prior to becoming pregnant. We continue to encourage all women who could become pregnant to take a daily supplement, as recommended above. We caution against taking more than one multivitamin tablet a day, as excess amounts of certain vitamins can be toxic.

It has been suggested that the federal government consider increasing the level of mandatory fortification. At this time, there is no strong evidence that higher levels of food fortification with folic acid will result in a further decline in rates of NTDs, or will result in lower rates of other birth defects. Possible risks associated with higher levels of fortification must also be considered. It is therefore prudent to maintain the fortification level as is.

It is nevertheless important for the research community to study this topic further. More research is also needed into the effect of folic acid and multivitamin supplement use on rates of other birth defects, given that food fortification is in place.