Prepregnancy Body Mass Index and Risk of Childhood Asthma

To study the association between prepregnancy BMI and the development of asthma in children.

Mothers and their children who were a part of Kaiser Permanente Northern California integrated health system were included in the study. Mothers enrolled included those who gave birth between January 1, 2005 through January 1, 2014. Children with cystic fibrosis were excluded from the study.

Mother-child pairs were followed for at least 4 years after birth and at 4, 6 and 8 years of age. BMI was calculated based on maternal weight and height and was classified as underweight, normal, overweight, or obese classes 1, 2, or 3 based on Centers for Disease Control and Prevention guidelines. The primary outcome, asthma, was met if patients had a primary diagnosis of asthma during an inpatient hospitalization or a secondary diagnosis with the primary diagnosis being respiratory distress, or two outpatient encounters with asthma as a diagnosis and evidence of at least two maintenance asthma medications filled, one being in the last year. A less stringent asthma definition was also used for comparison. Patients were followed at 4, 6 and 8 years of age. Findings were adjusted for gestational weight gain (GWG), gestational age and child’s BMI to determine whether these were confounders on the association between BMI and asthma in children.

A higher relative risk for developing asthma was noted with higher BMIs in the categories of overweight and obese classes 1, 2, and 3 when compared with normal BMIs. Using the less stringent asthma definition, investigators also found similar results with greater precision because of larger sample size, as it included a larger number of patients who met the asthma definition. Additionally, across all age cohorts, as prepregnancy BMI increased, the risk for asthma also increased, which was notable as BMI rose from 18 to 30 kg/m² in those 4 years of age and from 20 to 35 kg/m² in those 6 years of age.

There was an association between higher maternal prepregnancy BMIs and asthma in children which was consistent at different age groups. Overall GWG and gestational age did not impact these findings.

This study supported previously reported associations between higher maternal BMIs and asthma in children while taking into account possible confounders like GWG, gestational age and child’s BMI. Further studies are needed to better understand the biological relationship between higher BMIs and the development of asthma.