A gradual fixation method for chromosomal preparations of human oocytes.

Eleven oocytes were recovered after follicle aspiration carried out in nine women during laparoscopy or laparotomy. All oocytes were classified as preovulatory, judged by the fully dissociated cumulus. After elimination of the cumulus, ten of the oocytes exhibited the first polar body, and one was degenerated. A gradual fixation method was used for the chromosomal preparation of the oocytes. The quality of the preparations was improved, compared with the previously used air-drying technique. Nine of ten preparations from oocytes with first polar body displayed chromosomes. These sets consisted of well-spread meiotic chromosomes, and in six of them the chromosome complements of the first polar body could be seen, although quite distinct from the oocyte complement. Of eight preparations where the chromosomes could be counted, six showed 23 chromosomes, and two were abnormal, showing 21 and 16 chromosomes.