- The more overweight a woman is before getting pregnant,
the greater her risk of having a baby with a severe birth defect, according
to new Canadian research. The study, published in the medical journal Obstetrics
and Gynecology, also found that fortification of refined flour with folic
acid, a public-health measure that has sharply reduced neural-tube defects
such as spina bifida, has had a far lesser impact on the babies of obese
women."All weight groups benefit from folic-acid fortification, but
women in the highest-weight groups benefit the least," Dr. Joel Ray,
a clinician-scientist at St. Michael's Hospital in Toronto, said in an
interview. He said there are many possible explanations for this phenomenon.
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- First, women who are overweight or obese can be prediabetic,
and diabetes is a risk factor for birth defects. Second, it is possible
that the heavier a woman is, the more folic acid she needs. And third,
women who are obese are more likely to be poor, have less education and,
as a result, less likely to take multivitamins containing folic acid.
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- (It is recommended that all women of childbearing age
-- whether they are trying to get pregnant or not -- get at least 0.4 milligrams
of folic acid daily. Folic acid is a synthetic version of folate, which
is found in leafy greens, legumes such as lentils and kidney beans, and
orange juice. It is added to products made with refined flour, such as
white bread and white pasta, and to cornmeal. Most multivitamins contain
0.4 mg of folic acid, as well.)
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- Since fortification began in 1998, the incidence of neural-tube
defects in Canada has fallen by half, with some conditions, such as spina
bifida, falling 75 per cent; the incidence of the common childhood cancer
neuroblastoma has dropped by 60 per cent.
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- Because people who are obese often eat a diet rich in
starchy foods, such as white bread, pasta and baked goods, researchers
initially believed that fortification would greatly benefit obese women
who became pregnant.
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- But the new study suggests that the damage wrought on
the fetus by fat outweighs the benefits of folic acid.
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- Still, despite the clear link between being overweight
and neural-tube defects, Dr. Ray said pregnant women should not diet or
lose weight because that risks doing more harm than good. The neural tube,
which later becomes the baby's spinal cord, spine and brain, forms in the
first 28 days after conception, a time when most women don't yet know they
are pregnant.
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- "Weight loss during pregnancy will not make a positive
difference," he said. There is also no evidence that weight gain during
pregnancy increases risk. Rather, Dr. Ray said, the research should serve
as a reminder that maintaining a healthy weight and healthy diet has many
health benefits, to both a woman and her baby.
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- The study showed that a woman weighing 85 kilograms (187
pounds) has more than three times the risk of a having a baby with a neural-tube
defect as a woman weighing 52 kilos (115 pounds). Or, put another way,
for every 10 kilos of extra weight she is carrying, a woman's risk increases
20 per cent.
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- The study was conducted using records from all Ontario
women who underwent maternal screening during their pregnancies between
1994 and 2000.
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- There are three principal neural-tube defects: spina
bifida, when the spinal cord and backbone don't develop properly; anencephaly,
when the brain doesn't fully develop; and encephalocele, when a portion
of the brain protrudes from the skull.
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