Severe thrombotic events following ovarian stimulation for in-vitro fertilization (IVF) procedures in three women are reported. None of these patients presented any concomitant clinical sign of ovarian hyperstimulation syndrome. Coagulation inhibitors were in the normal range but cardiovascular risk factors were present. It is postulated that early thrombosis could be favoured by high endogenous plasma oestrogen concentrations subsequent to ovarian stimulation when associated with another risk factor. Our data are discussed in relation to previous publications. It is suggested that risk factors must be considered individually before each IVF attempt. In patients at high risk, clinical management of the post-transfer period is recommended.

Chromosome analysis of oocytes uncleaved after IVF allows the cause of the failure of cleavage to be determined and shows the incidence of chromosome disorders among human oocytes. A total of 198 uncleaved oocytes fixed 40 h after insemination were successfully analysed according to Tarkowski's air-drying method: 78.3% were unfertilized and arrested in metaphase II. Among them, 70% were normal (23,X) and 30% aneuploid (16% were hypohaploid, 14% were hyperhaploid). The incidence of chromosome breaks was 18%. In 12.1% of the oocytes, sperm chromosome condensation appeared premature usually in the G1 phase. This was especially observed in idiopathic infertility (7% of fertilized oocytes versus 2% in tubal infertility cases). In 8.1% of the cases, chromosome analysis showed diploidy which may be interpreted by either an absence of extrusion or a reintrusion of the polar body or by first cleavage failure during mitosis. In 1% of the cases triploidy was observed. Our results show that the main reason for failure of cleavage is related to failure of fertilization (78.3%). However, premature condensation of sperm chromosomes at the G1 phase appears to be quite frequent. This may be involved in the aetiology of some cases of idiopathic infertility. Finally, the high rate of chromosomal disorders (30%) in human oocytes may explain the high rate of chromosomal abnormalities in preimplantation embryos.

This study was designed to compare both the effectiveness and safety of two low-dose gonadotrophin regimens (step-up versus sequential step-up and step-down) for ovulation induction in polycystic ovarian syndrome (PCOS) patients. In all, 56 infertile clomiphene citrate-resistant PCOS patients were included in this prospective randomized study. A total of 38 cycles were conducted with a classic step-up protocol, whereas for 35 cycles the follicle-stimulating hormone (FSH) threshold dose was reduced by half when the leading follicle reached 14 mm in diameter (sequential protocol). Serum oestradiol, progesterone and luteinizing hormone concentrations and follicular growth rate were evaluated during the cycle. At the time of human chorionic gonadotrophin administration, cycles treated with sequential protocol exhibited significantly lower oestradiol concentrations [434 +/- 45 versus 593 +/- 67 pg/ml (mean +/- SEM)] and the number of medium-sized (14-15 mm) follicles was significantly reduced (0.3 +/- 0.1 versus 0.8 +/- 0.2) compared with cycles treated with the classic step-up protocol. Moreover, in these cycles serum luteal oestradiol concentrations were decreased significantly (350 +/- 77 versus 657 +/- 104 pg/ ml) compared with the classic step-up protocol. A sequential step-up and step-down protocol seems to be a safe and effective regimen for ovulation induction in PCOS patients. Decreasing the FSH dose following step-up follicular selection may be an alternative method to avoid multifollicular development.

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