Being obese during pregnancy dramatically increases the risk of the child developing asthma by their tenth birthday, according a study published online in the Journal of Allergy and Clinical Immunology.
Researchers from Melbourne and Sweden measured the body mass index (BMI) of almost 130,000 Swedish women in the early stages of pregnancy and found children of very obese women were 57% more likely to develop asthma than children whose mothers were a healthy weight.
The study’s lead author, epidemiologist Dr Adrian Lowe from the Murdoch Childrens Research Institute and the University of Melbourne, explains the impetus for the research and its findings:
The rates of both asthma and obesity have increased dramatically over the past five decades, which raises questions about a possible link between these two epidemics.
One of the consequences of rising rates of obesity in western societies is that mothers are increasingly starting their pregnancies either overweight or obese. This increases the risks of pre-term birth, the need for interventions such as caesarean sections, as well as the complications of gestational diabetes and hypertension (high blood pressure).
So how does maternal obesity impact on a child’s risk of asthma?
We examined the relationship between the mother’s body mass index (as a marker of overweight or obesity) in the first trimester of pregnancy, along with the risk of her child developing asthma in the first ten years of their life.
We collected information on the height and weight of all new mothers in Stockholm, Sweden between 1998 and 2009, during the first trimester of their pregnancy. We also monitored their children (almost 190,000) to see which ones required asthma medication or hospitalisation for asthma.
We found a very clear, linear pattern: as the mother’s weight increases above the normal range, the risk of asthma in the child increases. The children of very obese mothers – those with BMI of 35 or above during early pregnancy – had the highest risk of asthma.
But even children of mothers who were slightly overweight – with a BMI of between 25 and 30 – had a small increased risk of asthma when compared with mothers who were in a healthy weight range during early pregnancy.