Weight management strategies during pregnancy reduce child cardiometabolic risk. However, because maternal weight has an overall positive correlation with offspring bone mass, pregnancy weight management could adversely affect child bone health. We aimed to estimate associations between gestational weight gain (GWG) and bone mineralization in the offspring at 7 years of age, and test early pregnancy body mass index (BMI) as an effect modifier. We analyzed prospective data from 2167 mother‐child pairs from the Generation XXI birth cohort who underwent whole‐body dual‐energy X‐ray absorptiometry at 7 years of age. GWG was analyzed as a continuous measure and using the Institute of Medicine categories. In the whole sample and for each early pregnancy BMI category (under/normal weight and overweight/obese), relationships between GWG and offspring bone measures (bone mineral content [BMC], bone areal density [aBMD], size‐corrected BMC [scBMC], and height) at 7 years were fitted through local polynomial regression and smoothing splines. The magnitude of associations was estimated through linear regression coefficients (95% CIs), crude and adjusted for maternal age, height, educational level, and child gestational age. In under/normal weight mothers, GWG was associated with slightly increased bone measures at 7 years (per 5 kg of GWG, BMC:​ 0.07 SD [95% CI, 0.01 to 0.12];​ aBMD:​ 0.10 SD [95% CI, 0.05 to 0.15], scBMC:​ 0.11SD [95% CI, 0.06 to 0.16], and height:​ 0.05 SD [95% CI, 0.00 to 0.10]), while in overweight/obese mothers no effect of GWG on bone was observed (BMC:​ 0.02 SD [95% CI, –0.04 to 0.09];​ aBMD:​ 0.02 SD [95% CI, –0.04 to 0.08], scBMC:​ 0.01 SD [95% CI, –0.06 to 0.08], and height:​ 0.02 SD [95% CI, –0.04 to 0.08]). Also, no advantageous effect of gaining weight above the Institute of Medicine recommendations was observed in either early pregnancy BMI group. Our results suggest that adherence to Institute of Medicine recommendations for pregnancy weight gain is unlikely to have a negative repercussion on offspring bone health, particularly in women with excess weight in early pregnancy.