In Reply We thank Dr Luo and colleagues for commenting on our recent systematic review and meta-analyses and for acknowledging its robust methodology.1 Regarding their points on the potential effects of maternal age on gestational weight gain (GWG), it is plausible that demographic factors, including age, may influence intervention responses and associated outcomes. Our meta-analysis was restricted to examining the aggregate results published by the included studies because we did not have individual patient data from the 117 randomized clinical trials; as such, associations with maternal age could not be specifically explored. Dr Luo and colleagues cited 2 studies with modest sample sizes (1950 and 159 participants) to support their comments.2,3 In contrast, our 2017 individual patient data meta-analyses across 36 randomized clinical trials of antenatal lifestyle interventions in 12 526 women4 found no significant association with GWG (−0.03 kg [95% CIs, −0.08 kg to 0.02 kg] per 1 year increase in age) nor other key demographic variables, including body mass index (calculated as kg/m2), ethnicity, parity, or relevant underlying medical conditions. These findings were consistent when continuous covariates were analyzed as categorical measures based on clinically relevant cut points.