Aug. 15, 2011 -- Children of women who are overweight or obese when they become pregnant may be more likely to have asthma by the time of adolescence, a new study shows.
Researchers in Britain, Finland, and Sweden say their study suggests that being overweight during pregnancy may interfere with normal fetal development, though it does not prove a cause-and-effect relationship.
The study found that asthma-like respiratory symptoms such as wheezing were up to 30% more likely when children were teenagers if mothers were overweight or obese during fetal development.
The researchers write that the prevalence of children's asthma has risen substantially worldwide since the 1970s and that up to 37% of teenagers may have symptoms of asthma.
Though the reasons for increased asthma cases and symptoms are not completely clear, it appears that environmental factors may play a key role, according to the researchers. One reason may be that the prevalence of overweight and obese mothers also has risen dramatically.
The scientists examined the respiratory health of about 7,000 teenagers, 15 and 16, all born in northern Finland between July 1985 and June 1986.
Their mothers were questioned about their lifestyles, social backgrounds, and educational attainment when they had been pregnant for 12 weeks.
Information also was provided by medical professionals on the height and weight of the women before pregnancy and the medical history of their parents.
The researchers found that:
One in 10 of the teens wheezed and one in five had wheezed at some point.
6% had asthma, and one in 10 had been diagnosed with asthma at some point.
Teens whose mothers had been seriously overweight or obese before they became pregnant were 20% to 30% more likely to wheeze, have wheezed, or had asthma currently or previously.
Teens whose mothers were among the heaviest were 47% more likely to have severe wheezing difficulty.
The researchers say their findings do not show that prepregnancy obesity definitely causes respiratory symptoms among teens.
Obesity During Pregnancy
The researchers say other studies have shown links between maternal obesity and numerous complications during pregnancy.
Being overweight during pregnancy may interfere with normal development of a fetus as a result of disrupted metabolic, hormonal, or ovarian activity, according to the researchers. Also, increasing weight is linked to increasing levels of the hormone leptin, receptors for which are found in the lungs of developing fetuses.
They conclude that their research suggests that increases in rates of children's asthma and its symptoms may be at least partly related to the rapid rise in obesity in recent years.
The study is published online in the Journal of Epidemiology and Community Health.