Maternal pre-gravid obesity and early childhood respiratory hospitalization: a population-based case-control study.

Inflammation in utero is linked to childhood respiratory and infectious complications. Obesity is an increasingly common chronic inflammatory state, yet little is known about its role in childhood respiratory illness. We sought to examine the association between maternal pre-gravid BMI and early childhood respiratory hospitalization. We conducted a population-based case-control study using the Washington State Comprehensive Hospital Abstract Reporting System and linked birth certificate data. Cases were children age 0-5 years, born in Washington state, with a respiratory hospitalization between 2003 and 2008. We identified 15,318 cases, frequency matching each case to two controls by birth year (total 31,060 controls). We used logistic regression to estimate the risk (approximated by odds ratios) of early childhood respiratory hospitalization according to maternal pre-gravid body mass index (BMI) category (underweight, normal, overweight, obese), after adjustment for maternal and infant characteristics. An elevated maternal pre-gravid BMI was associated with increased risk of childhood respiratory hospitalization, with an adjusted odds ratio OR [95 % CI] = 1.08 [1.03-1.14] for overweight mothers (BMI 25-29.9 kg/m(2)), and OR = 1.29 [1.22-1.36] for obese mothers (BMI ≥ 30 kg/m(2)). An elevated maternal pre-gravid BMI was associated with higher risk of early childhood respiratory hospitalization. Childhood respiratory illness may be an important complication of excess maternal weight that should be shared with expectant mothers.