lasting effects not just on her own health but on the respiratory health
of her children as well.
"Children with asthmatic parents are at an increased risk of asthma if
the mother is overweight before pregnancy," said H.A. Smit, head of the
department of prevention and health services research at the National
Institute of Public Health and Environment in the Netherlands.
In fact, Smith and his fellow researchers found that the risk of asthma
is 65 percent higher among the offspring of overweight mothers if one or
both of the child's parents have a history of the disease.
Smit was to present the findings Tuesday at the American Thoracic
Society's annual meeting in San Diego.
As many as 20 million Americans have been diagnosed with asthma, about
9 million of them children, according to the American Academy of Allergy,
Asthma & Immunology. Despite advances in treatment, asthma is still
responsible for about 5,000 deaths each year in the United States, it
says.
Not all children born to parents with asthma go on to develop the
airway disease. That happens about 40 percent of the time, the academy
reports.
Because the exact causes of asthma are not clear, researchers have
looked at a number of factors that might contribute to its development,
including maternal smoking, the child's environment and more.
Smit's study sought to assess whether a mother's weight before
pregnancy could affect a child's risk for asthma. The study included
nearly 4,000 children, who were followed from birth to 8 years of age.
The mothers in the study averaged 30 years old, and almost 21 percent
were overweight � which the researchers defined as have a body mass index
higher than 25 � before becoming pregnant.
Children were considered to have asthma if their parents reported that
they'd had at least one attack of wheezing or shortness of breath or had
needed inhaled corticosteroids in the previous year. About 14 percent of
the children had asthma by age 8.
The researchers adjusted the data to account for confounding factors,
such as maternal education, mode of delivery, maternal smoking during
pregnancy, duration of breast-feeding, birth weight and the child's
current weight, according to Smit.
Although they found no association between maternal weight in children
born to parents without asthma, children born to parents with asthma who
also had an overweight mother had a 65 percent increased risk of
developing asthma.
Though the study was not designed to determine why being overweight
might affect a child's risk for asthma, Smit theorized that inflammation
could be the connection between the conditions. That's because obesity can
encourage inflammation, and inflammation is at the root of asthma.
Dr. Jennifer Appleyard, chief of allergy and immunology at St. John
Hospital and Medical Center in Detroit, said that "we don't know exactly
what causes or contributes to asthma, but it does look like there are some
things that occur in utero that could affect the child later."
But, she said, it may not be the fact that mothers are overweight. It
could be something that they're eating that's affecting their children.
It's just not clear from this study, she said, adding that that more
research needs to be done.
More information
The U.S. National Heart, Lung, and Blood Institute has more on the
causes of asthma.
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