METHODS OF STAGEING PRENATAL DEVELOPMENT IN COMPARATIVE EMBRYOLOGY

Modern research in regenerative medicine and xenotransplantation requires interdisciplinaryintegration with embryology, histology, biology, anatomy and physiology. The mostimportant basis for combining this knowledge is an adequate methodology for comparisonand standardization of research. The methodology of staging embryonic development usesthe segmentation of ontogenesis into successive stages, which are represented by timeclusters with certain morphological transformations. Ontogenetic development involvescontinuous changes, and during morphological studies, stages are compared in diff erentspecies, taking into account the presence of polymorphism and interspecifi c features,standardization of comparative morphology is the basis for obtaining adequate results. The objective of the work – to summarize and perform a comparative analysis of modern information on the staging of the prenatal period of human and mammalian ontogenesis.Based on their own morphological studies, scientists point to the variability of the internal and external structure for each Carnegie stage, in particular, the discrepancy between age indicators and the number of somites. Therefore, in publications, individual variations of morphometric results for each stage can be found. In modern studies, the results of morphometric indicators of R. O’Rahilly and F. Müller are more often used. The Carnegie scale uses the length of the embryo to determine age. In recent years, due to technological progress, determining the Carnegie stage of embryonic development by such a morphometric indicator as the length of the embryo has become more accurate. But when using clinical methods of antenatal diagnosis, there is no single consensus on the parameters that have the highest probability and allow a clear determination of the stage of embryos. The parietal- coccygeal distance is a generally accepted morphometric indicator. It is determined not only in classical anthropometric studies, but can also be measured during sonoembryological research. Currently, most scientists recommend using data from the 2010 edition of R. O’Rahilly for staging according to the Carnegie stages.Conclusions. 1. The most appropriate system for staging intrauterine development for comparative embryological studies of humans and mammals is the Carnegie stages. 2. The age of intrauterine development alone cannot be a determining indicator, since there may be individual morphometric diff erences in the length of the embryo and variants of the structure in embryos of the same gestational age. 3. Determining the correspondence of external and internal morphological features of stages is the most important criterion for comparative morphology, as it allows for interpolating research into identical stages of diff erent mammalian species. 4. Sonoembryology, as a method of prenatal ultrasound examination, in combination with classical methods of morphological examination, allows to improve signifi cantly prenatal diagnostics of the fetus.