AIMS: There is no previous study comparing the predictive ability of maternal pre-pregnancy body mass index (BMI) versus a 75-g oral glucose tolerance test (OGTT) in early pregnancy for large-for-gestational-age (LGA) infants. METHODS: This multi-institutional prospective cohort study included 966 pregnant Japanese women. A multiple logistic regression model was applied to compare the effect size of pre-pregnancy BMI, fasting plasma glucose (PG), and 1- and 2-h PG levels after a 75-g OGTT performed before 22weeks gestation for LGA. After these variables were included separately into the model as per continuous variables 1 standard deviation (SD) increase, they were included simultaneously. RESULTS: When pre-pregnancy BMI, fasting PG, and 1- and 2-h PG after a 75-g OGTT were separately included in the model, the adjusted odds ratios (ORs) for LGA per 1 SD increase in pre-pregnancy BMI, fasting, and 1- and 2-h PG were 1.55 (95% confidence interval [CI]: 1.26-1.91), 1.26 (95% CI: 1.03-1.54), 0.99 (95% CI: 0.78-1.25), and 1.17 (95% CI: 0.93-1.49), respectively. When these variables were included simultaneously, the adjusted ORs per 1 SD increase in pre-pregnancy BMI, fasting, and 1- and 2-h PG were 1.52 (95% CI: 1.23-1.88), 1.19 (95% CI: 0.96-1.46), 0.77 (95% CI: 0.57-1.03), and 1.30 (95% CI: 0.96-1.76), respectively. CONCLUSIONS: Maternal pre-pregnancy BMI was more strongly associated with LGA compared with a 75-g OGTT in early pregnancy. Health-care providers should recognize that women with a higher pre-pregnancy BMI carry a higher risk for having LGA infants regardless of the results of a 75-g OGTT.