AbstractBackgroundMaternal pre‐pregnancy body mass index (BMI) and gestational weight gain (GWG) have been linked to offspring allergic disorders. However, associations observed in previous studies were inconsistent and might be confounded by unmeasured familial factors. We aimed to examine the associations of maternal weight with offspring allergic disorders by using paternal BMI as a negative control exposure.MethodsWe included the data of 10,522 children from the Born in Guangzhou Cohort Study, 2012–2017. Data on maternal weight were obtained from questionnaires and obstetric records, and paternal weight was collected from questionnaires. Atopic dermatitis (AD) and wheezing at the age of 1 year were defined according to parent‐reported physician diagnosis. Risk ratios (RRs) were estimated by log‐binominal regression with mutual adjustment for maternal and paternal weight status.ResultsBy the age of 1 year, 16.2% and 7.9% of children were diagnosed with AD and wheezing, respectively. While maternal pre‐pregnancy BMI as a continuous variable was not associated with offspring AD, infants of pre‐pregnancy overweight/obese women had a higher risk of AD than those born to normal weight women; no such associations were observed for paternal BMI. Both maternal pre‐pregnancy BMI and paternal BMI were positively associated with the risk of offspring wheezing. Maternal GWG was not associated with AD or wheezing.ConclusionsOur findings suggest that maternal pre‐pregnancy overweight/obesity might increase the risk of infant AD via intrauterine mechanisms, whereas the association with wheezing might be confounded by uncontrolled familial factors. These findings may be valuable in early‐life prevention for offspring allergic diseases.