The specific features of intrauterine development and pheno- and genotypic characteristics were studied in newborn infants with duodenal atresia. Main anthropometric parameters at birth (weight, height, and head and chest circumferences), concomitant developmental malformations, gene frequencies and phenotypic combinations of ABO and Rhesus factor blood groups were analyzed. The babies with duodenal atresia were found to have considerably impaired intrauterine development, multiple concomitant hypoplastic developmental abnormalities, significantly higher frequencies of the ORh+ phenotype, and lower frequencies of the ARh+ phenotype.