MONDAY, Aug. 15 (HealthDay News) -- Teens of mothers who were overweight or obese when they became pregnant may be at increased risk for asthma symptoms, according to a new study.

It included nearly 7,000 teens aged 15 and 16 who were born in northern Finland between July 1985 and June 1986. The researchers also looked at health information collected from the teens' mothers, including height and weight before pregnancy.

About 10 percent of the teens had wheezing, about 20 percent had wheezing at some point, 6 percent had asthma and 10 percent had asthma at some point. After accounting for a number of other factors, the researchers found that a mother's weight before she became pregnant had a strong effect on a teen's wheeze/asthma risk.

Teens were 20 to 30 percent more likely to wheeze/have a history of wheezing, or to have asthma or a history of asthma, if their mothers were seriously overweight or obese before pregnancy.

Every excess kilogram (1 kilogram = 2.2 lbs) of weight on the mother at pregnancy was linked with a 2.7 to 3.5 percent increased risk of wheeze and asthma among teens, the researchers from Imperial College London calculated.

And after other factors were accounted for, teens with the heaviest mothers had a 47 percent increased risk of severe wheezing.

The study appears online in the Journal of Epidemiology and Community Health.

The hormonal and metabolic effects of being overweight during pregnancy may interfere with normal fetal development, including the lungs, the researchers suggested.

More information

The March of Dimes has more about obesity and pregnancy.