Objective The main objective of this study was to evaluate the effect of the ADIPOQ rs2241766, LEP rs7799039, and FTO rs9939609 polymorphisms on the birth weight status of Brazilian infants. Methods This cross‐sectional study was conducted in southern Brazil. Large for gestational age (LGA) newborns (n = 105), and the same number of small for gestational age/adequate for gestational age newborns, were included. Genotyping of the rs2241766, rs7799039, and rs9939609 polymorphisms was done by PCR‐RFLP analysis. Logistic regression was used to investigate the association between LGA newborns and the presence of the polymorphisms. Results Infants carrying the GG genotype of the rs7799039 polymorphism were 2.12 times more likely to be born LGA than those carrying the GA + AA genotypes (95% CI: 1.17–3.83). These results did not change substantially after adjusting for potential confounding variables (OR = 1.98; 95% CI 1.05–3.73) and adjustment for the three polymorphisms (OR = 1.98; 95% CI 1.05‐3.74). Regarding the ADIPOQ polymorphism, newborns carrying the TG or GG genotype were 1.88 times more likely to be born LGA than those carrying the TT genotype, although this difference was not statistically significant (p = 0.082). No association was found between the FTO gene polymorphism and newborn weight status. Conclusions This study showed that the GG genotype of the LEP polymorphism rs7799039 is a risk factor for LGA infants. The exact role and mechanism of action of the GG genotype of this polymorphism in weight status control remain to be elucidated, and more studies are needed.