The extent to which the morphology of the oocyte at the light microscopy level is related to the results of intracytoplasmic sperm injection (ICSI) is controversial. In this study, after cumulus removal, oocytes were graded into four groups according to the status of the first polar body, size of the perivitelline space and the presence of cytoplasmic inclusions. Oocyte data from 65 consecutive patients were reviewed. The results showed that, for oocytes without cytoplasmic inclusions, the fertilization rate and embryo development beyond 2-cell stage were significantly lower (P < 0.01) in the oocytes at grade 1-2 (poor) than those in oocytes at grade 3-4 (good). Grade 4 oocytes without inclusions gave the highest proportion (66.7%) of good embryos with grading 1-2 (grade 1 best; P < 0.01). A higher proportion of grade 1-2 oocytes (44.7%; P < 0.05) was obtained from patients older than 35 years. More oocytes containing cytoplasmic inclusions were seen in patients diagnosed as having female factor infertility (24.9%; P < 0.01) and older than 35 years (26.5%; P < 0.05) compared to patients with male factor infertility and younger than 35 years. The fertilization rate and embryo development were not associated with the oestradiol concentration on the day of human chorionic gonadotrophin administration or the total number of oocytes retrieved. The results suggest that human oocyte grading based on the triple factors first polar body, size of perivitelline space and cytoplasmic inclusions is related significantly to fertilization rate and embryo quality after ICSI.

A small proportion (about 17%) of experimentally produced tetraploid blastocysts are capable of postimplantation development in the randomly bred Q strain of mice. Four newborn mice, three of which were confirmed as tetraploid, were produced but all were eaten by their mother within a few hours of birth. Studies on the embryonic development of tetraploid mice reveal a variety of developmental abnormalities, especially during the later stages of gestation. At 14 1/2 and 16 1/2 days, tetraploid embryos weigh significantly less than corresponding stage diploids, especially so if litter size is taken into account. Histologically, aberrations are found in many different tissues with a clear hierarchy of susceptibility shown among the organs. For instance, yolk-sac-derived blood, and gonads, are invariably affected and the anterior end of the neural tube also seems to be particularly at risk. Possible explanations for the aberrant development are discussed and it is concluded that strictly genetic reasons can be ruled out and that physiological difficulties imposed by the increased size of tetraploid cells and/or problems produced by lack of cell numbers are instrumental in causing abnormal development. Using weight as a guide it is estimated that tetraploid embryos at 14 1/2 and 16 1/2 days gestation contain about one-quarter as many cells as similar stage diploids.