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The influence of semen quality on fertilization rates in an in-vitro fertilization (IVF) programme was studied by analysing both conventional semen parameters and computerized movement characteristics. The study was based on 407 inseminated oocytes which were obtained from 50 patients in 113 laparoscopies. Sperm concentration did not correlate strongly with the fertilization rate. Sperm motility and morphology were the most meaningful parameters in predicting fertilization success. A drop in fertilization rate was found when sperm motility or normal morphology were below 40%. Sperm velocity measured in semen was the only sperm movement parameter which correlated with the fertilization rate, albeit weakly. The latter was reduced when average sperm velocity in semen was less than 50 microns/sec. Conventional semen parameters seem to be more predictive of the fertilizing potential of an ejaculate than movement characteristics obtained by computerized image analysis.

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This study analysed data from 27 couples in an IVF-ET programme. The maternal age range was 28-43 years. Statistical analyses on 182 oocytes showed no maternal age effect on the number of oocytes, their stage of maturation or their fertilization rate. There was also no effect of age of either partner or of seminal parameters on the fertilization rate. In contrast, occurrence of diploid oocytes was confined to three of the older women. The proportion of failures of fertilization was significantly higher in immature oocytes. These failures, which included 18 uncleaved, multipronuclear or fragmented zygotes, were related to disturbances of oocyte maturation. Four (out of five) oocytes re-inseminated with fresh semen produced polyspermy. One zygote showed marked asynchrony in the development of the two pronuclei. In eight zygotes the paternal complements had an allocyclic pattern of chromosome condensation between and within chromosomes or chromosome regions. In two other zygotes the paternal complement showed one chromosome prematurely condensed. This single-chromatid chromosome would be lost in the following cleavage division, suggesting that aneuploidy due to 'anaphase lag' is not a rare event during embryo cleavage.