FERTILIZATION AND PREGNANCY USING METAPHASE-I OOCYTES IN AN INTRACYTOPLASMIC SPERM INJECTION PROGRAM

Purpose: In this study we investigated whether, metaphase I oocytes co llected in an intracytoplasmic sperm injection program could successfu lly be matured and fertilized by injecting aged (>20-hr) spermatozoa. Materials and Methods: Metaphase I oocytes aspirated were preincubated for 20 hr to allow the oocytes to reach meiotic maturity. Only metaph ase II oocytes were injected The original sperm sample processed on th e day of aspiration was used in the microinjection process. Results: O ne hundred eighty-three oocytes were collected, of which 42 (23%) were metaphase I oocytes. These were incubated for 20 hr and microinjected with the original sperm sample. Thirty-one (74%) of the metaphase I o ocytes reached meiotic maturity (extruded polar body); 67.7% showed tw o pronuclei 18 hr after injection and 61.3% embryo development 40 hr p ostinjection. No difference in fertilization and embryo development ra te was found in metaphase II oocytes injected 6 hr postaspiration vers us 20 hr postaspiration. An ongoing pregnancy was also achieved using only embryos obtained from matured metaphase I oocytes. Conclusions: M etaphase I oocytes can be successfully matured in vitro and injected r ising aged (>20-hr) sperm samples. Matured metaphase I oocytes, if suc cessfully injected produce embryos able to induce pregnancy.