TORONTO - It's been known for years that taking folic acid before and during pregnancy can prevent neural tube defects like spina bifida in newborns. But research suggests the B vitamin also appears to lower the risk of some potentially fatal congenital heart defects in children.
In a study published Monday in the journal Circulation, Canadian researchers examined the incidence of congenital heart defects in babies born after 1998, when Canada mandated that all flours, pasta and cornmeal be fortified with folic acid in a bid to prevent neural tube defects in offspring.
Folic acid, also known as folate or vitamin B9, helps the body produce and maintain new cells, as well as being involved with DNA repair. The presence of adequate folic acid during pregnancy is critical when cells are growing and dividing very quickly, as is the case when a woman's womb is expanding, the placenta develops and the fetus is growing.
Researchers analyzed records for almost six million Canadian births between 1990 and 2011 and found that folic acid food fortification was associated with an 11 per cent drop overall in rates of congenital heart defects in babies.
"The effect was seen with regard to several types of congenital heart defects, but not all types," Dr. K.S. Joseph, a professor in the school of population and public health at the University of British Columbia, said Monday from Vancouver.
For instance, food fortification with folic acid was linked to a 27 per cent drop in the proportion of babies born with heart outflow abnormalities and 23 per cent with a narrowed aorta, the major artery that carries blood to the rest of body. The incidence of atrial and ventricular septal defects — holes in the walls that separate the heart's chambers — fell by 18 per cent and 15 per cent, respectively.
However, no changes were seen in the rates of cardiac defects caused by chromosomal abnormalities or other anomalies of the heart and circulatory system.
"The mechanisms by which food fortification with folic acid is having this effect on congenital heart defects to some extent is unexpected," said Joseph, senior author of the Public Health Agency of Canada-sponsored study.
"But even where it was expected, with regards to prevention of neural tube defects, we don't fully understand the mechanisms," he said. "Each of these subtypes of congenital heart defect is caused by a different mechanism and why or how the folic acid increase would prevent them is really unknown."
Still, Joseph said there are factors that can mitigate against the benefits of optimal folic acid intake before and during pregnancy, both through fortified foods and daily supplements.
The researchers found that older maternal age, multiple fetuses, the existence of pre-pregnancy diabetes and preterm pre-eclampsia — factors that increased within the population between 1990 and 2011 — increased the rates of atrial septal defects. Only when women subject to those factors were removed from the analysis did researchers see a drop in the overall incidence of that particular heart defect in newborns.
The Society of Obstetricians and Gynecologists of Canada (SOGC) recommends women take a daily multivitamin containing folic acid before conception and during pregnancy to lower the risk of birth defects, including neural tube defects, heart and limb defects, urinary tract anomalies, narrowing of the lower stomach valve, and oral facial clefts such as cleft lip and cleft palate.
Joseph said all women of child-bearing age should be supplementing their diets with a minimum daily dose of 400 micrograms of folic acid, even before deciding to become pregnant. Some women with a high risk of having a child with a birth defect — for instance, with insulin-dependent diabetes or a family history of birth anomalies — may be advised by their doctor to take a higher dose.
"Because so many pregnancies are unplanned, the general advice is that for reproductive-age women who could become pregnant, they should be supplementing pre-conception," he said. "Well before they get pregnant, they should be taking folic acid."
About one per cent of babies in Canada are born with a congenital heart defect, many of whom are at risk for life-long disability or, in about 10 per cent of cases, premature death. An estimated 257,000 Canadians are living with congenital heart disease, requiring ongoing cardiac care, the Canadian Congenital Heart Alliance says on its website.
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