Human embryos derived from in vitro and in vivo matured oocytes: analysis for chromosomal abnormalities and nuclear morphology

PURPOSE: To determine whether embryos resulting from oocytes matured in vitro have a higher incidence of nuclear and/or genetic abnormalities compared to embryos resulting from oocytes matured in vivo. METHODS: Fluorescence in situ hybridization analysis for chromosomes X, Y, and 18 was used to compare the rates of aneuploidy, mosaicism, and nuclear abnormalities in embryos derived from oocytes that were prophase I at aspiration (immature group) to that observed in embryos resulting from oocytes that were metaphase I or II at aspiration (mature group). RESULTS: Based on nuclear morphology, significantly more embryos in the mature group (23%) were classified as normal compared to embryos in the immature group (3%). No difference was found in the rate of aneuploidy or in the incidence of mosaicism involving these chromosomes. CONCLUSIONS: These findings suggest that few embryos derived from prophase I oocytes collected following ovarian stimulation are morphologically normal.