[Optimizing ovarian stimulation for IVF using GnRH antagonists].

ART teams have failed to predict that pregnancy rates in GnRH antagonist regimens will be lower compared to the agonist regimens. No evidence appears to exist for an adverse effect of GnRH antagonists on oocyte/embryo quality. Abnormal development of endometrium at OPU is present in all cycles stimulated with GnRH antagonists and it is also encountered in all stimulation schemes using gonadotropins. Endometrium advancement is negatively associated with the probability of pregnancy. Endometrium histology at oocyte retrieval is positively associated with LH levels at initiation of stimulation and the duration of rec FSH stimulation prior to antagonist initiation. The presence of elevated serum progesterone on day two of the cycle is associated with a higher exposure to progesterone and a decreased probability of pregnancy. The higher the LH levels on day 8 of stimulation, the lower the probability of pregnancy. Low E2 levels on the day of hCG administration are not associated with a decreased probability of pregnancy. Ovarian stimulation for IVF alters steroid receptor kinetics in the follicular phase. Prolongation of follicular phase is associated with a decreased probability of pregnancy. Prolongation of follicular phase results in secretory changes of endometrium at OPU.