EPIGENETIC INFLUENCES ON OOCYTE DEVELOPMENTAL COMPETENCE - PERIFOLLICULAR VASCULARITY AND INTRAFOLLICULAR OXYGEN

Purpose: Studies indicating that the developmental competence of the h uman oocyte is influenced by the level of intrafollicular oxygen are d escribed Methods: Perifollicular vascularity and dissolved oxygen cont ent were determined by color Doppler ultrasonography and analysis of f ollicular fluid at ovum retrieval, respectively, in stimulated cycles for in vitro fertilization. Results: Differences in the degree of peri follicular vascularity correlate with differences in the dissolved oxy gen content of the corresponding follicular-fluid. Oocytes with cytopl asmic and chromosomal disorders and embryos with multinucleated blasto meres and limited developmental ability were derived predominantly fro m underoxygenated follicles. Findings from several studies indicate th at embryos with the highest implantation potential originate from foll icles that are well-vascularized and oxygenated. Conclusions: Follicul ar vascularity and oxygen content appear to be important determinants of oocyte competence. Possible causes of differences in follicle-speci fic vascularity and the potential effects of severe hypoxia on the nor mality of molecular and cellular processes during follicle growth and preovulatory development are discussed.