A study suggests apple-shaped women with a waist bigger than 88cm have a higher risk of developing asthma - even if they have a normal body weight.
Being overweight is well known to raise the risk of asthma.But the latest study suggests that the amount of weight women carry around the abdomen might be particularly important.
The study, by the Northern California Cancer Centre at Berkeley, appears in the journal Thorax.
The researchers analysed data on 88,304 female teachers and school administrators.
The results showed that overweight women were 40% more likely to have asthma than women of a normal weight.
Asthma was more than twice as likely in obese women, and more than three times as likely in extremely obese women than in those of normal body weight.
But perhaps more surprisingly, the researchers also found that women of normal body weight, but with a waist circumference of more than 88cm were also at increased risk - around a third higher than those with a smaller waist.
Overall, 5.4m people in the UK have asthma, and rates have been rising in recent years.
Body mass index (BMI) has been widely used as a standard measure of obesity.