Introduction: The goal of this study was to evaluate the association between maternal pre-pregnancy body mass index (BMI), gestational weight gain (GWG) and risk of childhood asthma/wheeze by conducting a meta-analysis of cohort studies. Methods: A systematic literature search of several databases was conducted through January 2020 to identify relevant studies. The exposure of interest was maternal pre-pregnancy BMI (e.g., underweight, overweight, obesity, and continuous BMI) and GWG (e.g., inadequate GWG, excessive GWG, GWG < 9 kg, GWG > 15 kg, and continuous GWG). Random-effects models were used to calculate the pooled odds ratios (ORs) and their 95% confidence intervals (CIs). Results: Twenty-one cohort studies were included (N = 150,198 mother-child pairs). Age of children was 3 months to 16 years. Maternal overweight (OR = 1.13; 95% CI: 1.07 - 1.19) and obesity (OR = 1.39; 95% CI: 1.23 - 1.58) were associated with higher odds of childhood asthma/wheeze; each 1-kg/m2 increase in maternal pre-pregnancy BMI was associated with a 4% increase in the odds of childhood asthma/wheeze. GWG < 9 kg (OR = 1.08; 95% CI, 1.01 - 1.14) was slightly associated with higher odds of childhood asthma/wheeze. Subgroup analyses have identified several variables associated with the between-study heterogeneity. Conclusions: Maternal overweight and obesity are associated with an elevated risk of childhood asthma/wheeze, suggesting that maternal pre-pregnancy BMI need to be considered in studies on the early origins of asthma. Further studies are needed to confirm the association between GWG and risk of childhood asthma/wheeze.