Influence of different stimulation treatments on oocyte characteristics and in-vitro fertilizing ability

A retrospective analysis was performed in order to compare the number and quality of oocytes recovered in in-vitro fertilization cycles according to different protocols for ovarian stimulation. Treatments including a gonadotrophin-releasing hormone agonist (GnRHa), either decapeptyl or buserelin, were associated with the recovery of more oocytes (6.0-7.2%) than treatments without GnRHa (3.7-4.8%). However, the mean number of normal embryos per patient yielding oocyte(s) was comparable between cycles stimulated with or without GnRHa (2.4-2.7), except in those cycles programmed with norethisterone and gonadotrophins (1.7). There was no difference in the rates of immature or atretic oocytes between stimulation treatments. Following clomiphene and human menopausal gonadotrophin treatment there was a lower rate of fractured zona oocytes, higher rates of fertilization and normal growth of fertilized eggs than after any other treatment. The proportion of normal embryos per recovered oocyte was inversely related to the degree of ovarian response in most of the stimulation treatments. Most of the abnormal embryos contained more than two pronuclei in cycles without GnRHa administration and exhibited polynucleated blastomeres in cycles treated with buserelin or decapeptyl. In conclusion, the use of GnRHa and gonadotrophins for ovarian stimulation increased the mean number of recovered oocytes, but did not increase the mean number of embryos able to develop.