Background and aimsEvidence on the association of maternal obesity with offspring cardiometabolic health is limited, particularly for the Asian population. We aimed to examine the associations of maternal body mass index (BMI) in early pregnancy and gestational weight gain (GWG) rate in mid- and late-pregnancy with childhood cardiometabolic traits. Methods and resultsWe used data of 1452 mother-child pairs from a population-based prospective cohort study in China. Maternal BMI in early pregnancy and GWG rate in mid- and late-pregnancy were calculated. Childhood cardiometabolic traits were assessed at aged 4–7 years, including BMI, BMI-z, systolic blood pressure (SBP), diastolic blood pressure, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, total cholesterol, triglycerides, fasting glucose, and C-reactive protein. Each 1 kg/m2 increase in maternal BMI in early pregnancy was associated with 0.46% (95% confidence interval, 0.19%–0.72%) higher children BMI, 0.05 (0.02–0.08) higher BMI-z, 0.41% (0.22%–0.59%) higher waist circumference, and 0.24% (0.03%–0.46%) higher SBP. Each 1 kg/week higher GWG rate in mid- and late-pregnancy was associated with higher children SBP (4.58% [1.46%–7.71%]), triglycerides (18.28% [3.13%–33.44%]), and fasting glucose (5.83% [2.64%–9.02%]) and lower BMI-z (−0.45 [−0.82 to −0.08]). Additional adjustment for offspring BMI attenuated the associations for maternal BMI but not for GWG rate. ConclusionsThe increase in maternal BMI and GWG are associated with adverse cardiometabolic profiles in childhood. The association between maternal BMI and childhood cardiometabolic traits is likely mediated using the offspring BMI.