A Study of Factors Affecting the Success of Human Fertilization in Vitro. I. Influence of Ovarian Stimulation Upon the Number and Condition of Oocytes Collected

Abstract

The degree of cumulus dissociation was estimated upon oocyte recovery at 35 .+-. 1 h following either the onset of the plasma luteinizing hormone (LH) surge or human chorionic gonadotropin (hCG) administration. The degree of cumulus dissociation, classified as either undissociated (0), moderately (+) or fully (++) dissociated, was 4.8, 4.8 and 90.4% in spontaneous cycles as compared to 5.0, 44.7 and 50.3% in cycles stimulated with clomiphene citrate or human menopausal gonadotropin (hMG). The lower rate of oocytes with ++ cumuli at collection in stimulated cycles (P < 0.001) was related to follicle growth stimulation but was not related to hCG administration. The treatments allowed the collection of more oocytes with expanded + or ++ cumuli (1.58 .+-. 0.13 vs. 0.77 .+-. 0.08, P < 0.01) although they did not increase the mean number of ++ cumulus oocytes (0.84 .+-. 0.09 vs. 0.73 .+-. 0.09, NS [not significant]). The proportion of laparoscopies resulting in the collection of one or more ++ cumulus oocytes was between 70 and 76% in spontaneous or stimulated cycles except when only one preovulatory follicle was observed in the stimulated cycles (31%, P < 0.001). At least 77.8, 29.3 (P < 0.01) and 6.8% (P < 0.001) of the oocytes surrounded by 0, + or ++ cumulus had not achieved meiotic maturity at the time of collection. The mean number of embryos grown in vitro following each laparoscopic attempt was not significantly increased by the treatment of patients (0.47 .+-. 0.07 vs. 0.31 .+-. 0.09 in stimulated or spontaneous cycles, respectively). The degree of cumulus dissociation seems to represent a criterion of maturity rather than of quality of the oocyte-cumulus complex. This criterion may be used to determine the optimum time interval between oocyte recovery and in vitro insemination.