The current knowledge allows for the definition of the genetic factors contributing to pathological body mass gain and obesity development. One of the possible candidates is the gene of β3-adrenergic receptor (ADRB3). Due to the fact that the basic function of this receptor is the induction of thermogenesis process and an increase of energy expenditure, the significance of Trp64Arg polymorphism of ADRB3 gene in disturbances of metabolic processes, which may induce disturbances of adipocytes function and lead to excessive body mass gain, obesity and early beginning of diseases connected with obesity (dyslipidemia, obesity, chronic hypertension, diabetes mellitus type II), has been suggested. The investigations performed in pregnant women concern, in the majority of cases, women with obesity, diabetes mellitus and gestational hypertension. These studies indicate the possible correlation of higher value of body mass index (BMI) with the presence of mutated 64Arg allele. In healthy pregnant women the relationship between Trp64Arg polymorphism of ADRB3 receptor and body gain has been suggested. Additionally, in female carries of the mutated 64Arg allele, a higher placenta mass and birth mass of newborns have been noted. This publication is merely single voice in the discussion because only one cause of excessive body gain and obesity presented here - Trp64Arg polymorphism of ADRB3 receptor. The problem seems to be more complicated and requires an investigation of the influence of other genetic and environmental factors, and the future populate investigations in Trp64Arg polymorphism of ADRB3 receptor.