OBJECTIVE: This study aimed to identify body mass index (BMI) growth trajectories from birth to 24 months of age and examine the independent and additive effects of four maternal metabolic risk factors, namely prepregnancy BMI, the rate of gestational weight gain, gestational diabetes mellitus (GDM) and gestational hypertension, on offspring growth trajectories in childhood in China. DESIGN: A retrospective cohort study was conducted. SETTING: The study used Maternal and Child Health Management Database in Chengdu, China, including the mothers' antenatal care data, birth certificate records and 0-3-year-old children's healthcare data. PARTICIPANTS: The study included mothers who gave birth between January 2014 and December 2014, and followed their offspring through 31 December 2016. The final analysis included 4492 mother-child pairs. PRIMARY OUTCOME MEASURES: The primary outcomes were children's BMI measurements from birth to 24 months of age. We performed group-based trajectories modelling to identify children's BMI growth trajectories. Then, we applied logistic regression to examine the associations between maternal metabolic risk factors and offspring BMI trajectories in childhood. RESULTS: Four distinct trajectories were identified: stable low (16.83%), stable average (40.69%), stable high (32.06%) and early increase (10.42%) trajectories. Relative to the stable average trajectory, maternal prepregnancy overweight (adjusted OR (aOR)=2.001, 95% CI 1.482-2.702, p<
0.001), an excessive rate of gestational weight gain (aOR=1.496, 95% CI 1.138-1.966, p=0.004) and GDM (aOR=1.470, 95% CI 1.097-1.970, p=0.010) were positively associated with their offspring being in the early increase trajectory. In addition, the children's risk of being included in the early increase trajectory showed an increasing trend with an increasing number of adverse maternal metabolic risk factors. CONCLUSION: Exposure to maternal prepregnancy overweight, excessive rate of weight gain and GDM resulted in a greater risk of offspring exhibiting an early increase trajectory for BMI. Decreasing maternal metabolic risk before and during pregnancy and monitoring childhood growth trajectories may prevent or delay the onset of childhood obesity.