Pathway between maternal obesity and childhood asthma nonallergic

Maternal pre-pregnancy bodyweight is associated with the risk for children developing asthma and wheezing by the age of 7 years, Danish research shows.

However, maternal obesity had no effect on the incidence of the allergic diseases atopic eczema and hay fever.

"The findings of this study lead us to hypothesize a nonallergic inflammatory pathway behind the associations between maternal obesity and respiratory symptoms," say Maria Harpsøe (Statens Serum Institut, Copenhagen, Denmark) and colleagues.

The study included 37,164 mothers enrolled in the Danish National Birth Cohort registry who had 38,874 children between 1996 and 2002. Mothers were asked about their health and their child's health twice during pregnancy, when the child was 6 and 18 months old, and again when the child was 7 years old.

During follow up, 10.4% of the children developed doctor-diagnosed asthma, with half having current asthma, while 29.3% experienced wheezing, according to their mothers. Meanwhile, 25.8% of children had atopic eczema at some point, and 4.6% had doctor-diagnosed hay fever.

There was a significant association between increasing pre-pregnancy body mass index (BMI) and the incidence of doctor-diagnosed asthma, such that children whose mothers had a pre-pregnancy BMI of 35 kg/m² or more had a 52% increased odds for diagnosis (15.1 vs 9.6%).

Increasing maternal weight gain during pregnancy also had a significant relationship with the risk for asthma diagnosis although this was greatly reduced when the authors accounted for confounding factors such as pre-pregnancy BMI.

While increasing pre-pregnancy BMI was associated with an increased risk for childhood wheezing, pregnancy weight gain showed no significant relationship.

Interestingly, mothers' pre-pregnancy BMI and maternal weight gain were not associated with atopic eczema or hay fever in their children.

Harpsøe and colleagues say that their study supports previous findings of a link between maternal BMI and asthma risk, but fail to evidence suggestions that this is mediated through an allergic pathway.

"However, adipokine and cytokine changes in obesity passed on from mother to child could explain some of the suggested effect of BMI and [maternal weight gain] on asthma and wheezing in the offspring," they write in the Journal of Allergy and Clinical Immunology.

They add that further research will be needed to explore how the findings can be used to improve children's respiratory health.

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