Journal of in Vitro Fertilization and Embryo Transfer, Vol. 2, No. 3, 1985 Abnormal Chromosome Behavior in Human Oocytes Which Remained Unfertilized During Human in Vitro Fertilization HORST SPIELMANN, I CHRISTIANE KROGER, MANFRED STAUBER, 2 and RICHARD VOGEL Accepted: May 16, 1985 (European Editorial Office) Chromosomal abnormalities and abnormal embryonic development have previously been observed after human in vitro fertilization (IVF). Chromosomal abnormalities may arise not only after fertilization but even earlier during meiotic maturation of human ooeytes in culture. Since chromosomal analysis is simple in oocytes during meiotic maturation, the chromosomal status was ana- lyzed in oocytes which remained unfertilized in a human in vitro fertilization program. In 50fertilization attempts the chromosomes of 62 unfertilized oocytes could be an- alyzed; 45 of them were in the process of meiotic matu- ration. In three oocytes two small polar bodies were ob- served 16-18 hr after insemination in the absence offer- tilization. In one oocyte abnormal chromosome behavior was found during the first meiotic division, and in four oocytes during metaphase of the second meiotic divi- sion. These data suggest that chromosomal analysis of unfertilized oocytes in human IVF may improve the un- derstanding of human oocyte maturation and fertiliza- tion. KEY WORDS: human IVF; abnormal oogenesis; cytogenetical analysis. INTRODUCTION Abnormal development of human preimplantation embryos was observed after in vitro fertilization (IVF) by both light and electron microscopy (1-3) and in cytogenetic studies (3-5). Such abnormali- ties of the earliest development of human embryos may be induced not only after fertilization in culture 1 To whom conespondence should be addressed at Max von Pet- tenkofer Institut des Bundesgesundheitsamtes, P.O. Box 33 oo 13, D-1000 Berlin 33, West Germany. 2 Department of Gynaecotogy and Obstetrics of the Freie Uni- versit~it Pulsstr., D-1000 Berlin 19, West Germany. but already during meiotic maturation of the oo- cytes which are collected from the ovaries before ovulation. Studies in laboratory animals such as in- vestigations of meiotic oocytes in rabbits (6), mice (7), squirrel monkeys (8), and first cleavage-stage mouse embryos after IVF (9) have indicated that hormonal induction of follicular development as well as culture systems can affect the chromosomes during meiotic maturation. Since there is no com- parable information on human oocytes and since such data may help to improve the IVF method in humans, a cytogenetic analysis was performed on oocytes that remained unfertilized in our human IVF program. MATERIALS AND METHODS Follicle stimulation and oocyte recovery followed the usual procedure (10), i.e., clomiphene citrate (100 mg daily) was given for 5 days starting on day 2 of the cycle, follicle growth was monitored by ultrasound, and laparoscopy was performed 28-36 hr after the injection of 5000 IU of human chorionic gonadotropin (hCG). Ham's F-10 supplemented with 10% human cord serum was used for oocyte re- covery, for preincubation of the oocytes, and for sperm preparation, insemination, and embryo cul- ture and transfer into the uterus of the mother. For ethical reasons it was agreed to include all oocytes which seemed morphologically normal in the IVF program, even those which did not show expansion of the cumulus cells. The oocytes were usually preincubated for 4-6 hr and 2 • 105 motile sperm were added to oocytes in 1 ml of medium in test tubes (1). Sixteen to ~ hours after insemination cumulus cells 138 0740-7769/85/0900-0138504.50/0 9 1985 Plenum Publishing Corporation