The placenta is a temporary fetal organ that is crucial for normal course of pregnancy. Serotonin, a hormone and a neurotransmitter, is involved in regulating the development and various functions of the placenta. A key catabolic enzyme of serotonin is monoamine oxidase (MAO), a flavoenzyme whose isoform MAOA is abundant in the placenta. The aim of this thesis was to contribute to a better understanding of the properties and regulation of MAOA in human placenta. For this purpose, a group of newborns (n=143) were genotyped for MAOA-uVNTR polymorphism, a potential candidate for regulation of transcriptional activity of MAOA gene. In placenta samples MAOA mRNA levels were determined using the reverse transcription-quantitative real-time PCR (RT-qPCR) method and the kinetic parameters (Vmax, KM) of MAOA were determined by the spectrofluorimetric method using kynuramine as a substrate. Placental MAOA mRNA levels did not differ depending on the MAOA-uVNTR genotype, suggesting that this polymorphism does not play major role in the regulation of MAOA gene expression in the human placenta. MAOA mRNA level and MAOA kinetic parameters did not differ between male and female newborns. A positive correlation was observed between MAOA mRNA levels and MAOA enzyme activity. The obtained results provide a basis for further research into the mechanisms of MAOA gene regulation in the human placenta and the potential role of this enzyme in various pregnancy complications associated with impaired placental function.