Associations between maternal body mass index and childhood infections in UK primary care: findings from the Born in Bradford birth cohort study.

OBJECTIVE: To explore associations between maternal body mass index (BMI) in early pregnancy and childhood infections. DESIGN: Birth cohort study linked to primary care records. SETTING: Bradford, UK. PARTICIPANTS: Live singleton births within the Born in Bradford cohort study between 2007 and 2011. EXPOSURES: Maternal BMI in early pregnancy. MAIN OUTCOME MEASURES: The total number of infections between birth and ~14 years of age with subgroup analysis by infection type and age. RESULTS: A total of 9037 mothers and 9540 children were included in the main analysis. 45% of women were of Pakistani ethnicity and 6417 women (56%) were overweight or obese. There was an overall trend for an increasing infection rate with increasing maternal BMI. In adjusted models, only those with obesity grade 2-3 had offspring with significantly higher rates of infection during the first year of life (RR 1.12 (95% CI 1.05 to 1.20)) compared with women of healthy weight. However, by age 5 to <15 years, children born to overweight women (RR 1.09 (95% CI 1.02 to 1.16)), obese grade 1 women (RR 1.18 (95% CI 1.09 to 1.28)) or obese grade 2 women (RR 1.31 (95% CI 1.16 to 1.48)) all had significantly higher rates of infection compared with those born to healthy weight mothers. Respiratory tract and skin/soft tissue infections made up the majority of excess infections. CONCLUSIONS: Maternal BMI was positively associated with rates of offspring infection in this study cohort, and suggests that we should be supporting women to achieve a healthy weight for pregnancy. Future research should investigate whether this is replicated in other populations, whether there is a causal association and the potential mechanisms and areas for intervention.