Human oocyte cytometry and fertilisation rate after subzonal insemination.

The cytometry of 545 oocytes was evaluated during subzonal insemination (SUZI; 85 attempts), on day 0 (egg retrieval and SUZI), day 1 and day 2 (embryo transfer). On day 0, the egg and oolemma diameters (mean +/- SD) were 164.0 +/- 19.6 microns and 114.2 +/- 16.8 mu 5m respectively. The zona thickness was 17.8 +/- 13.4 microns and correlated with the oolemma diameter (r = 0.24, p < 0.001). The fertilisation rate was significantly lower for the smaller oocytes (less than 108 microns diameter) compared with the larger oocytes (over 108 microns) (9.8% vs 21.2% respectively; p < 0.05). There was little variation in oocyte diameter according to nuclear status. However, oocyte diameter increased significantly between day 0 and day 1 (p < 0.001) for both fertilised and unfertilised oocytes. Six different indications for SUZI were investigated in detail: three with non-specific (normal and subnormal sperm with in vitro fertilization failure, oligoasthenospermia) and three with specific sperm defects (flagellar dyskinesia, absence of outer dynein arms, antisperm antibodies). Oocytes from the non-specific defect groups had significantly smaller diameters than the others (p < 0.05). The mean fertilisation rate was related to the mean oolemma diameter for the groups with non-specific sperm defects and the group lacking dynein arms (LODA) (r = 0.91, p < 0.05). Eggs from the groups of patients with LODA and those with antisperm antibodies had thicker zona pellucida than others (p < 0.05). These findings suggest that in addition to nuclear criteria of maturity, the growth of oocytes is an important factor for fertilising ability.(ABSTRACT TRUNCATED AT 250 WORDS)