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There is a high risk of obstetric complications in singleton oocyte donation pregnancies, but the perinatal outcomes are favourable. Patients should be counselled about these risks and monitored for these complications during pregnancy.

Maturation arrest of human oocytes may occur at various stages of the cell cycle. A total failure of human oocytes to complete meiosis is rarely observed during assisted conception cycles. We describe here a case series of infertile couples for whom all oocytes repeatedly failed to mature during IVF/ICSI. Eight couples, all presenting with unexplained infertility, underwent controlled ovarian stimulation followed by oocyte retrieval and IVF/ICSI. The oocytes were stripped of cumulus cells prior to the ICSI procedure and their maturity status was defined. In each couple, oocyte maturation was repeatedly arrested at the germinal vesicle (GV) (n = 1), metaphase I (MI) (n = 4) and metaphase II (MII) (n = 3) stage. Oocyte maturation arrest may be the cause of infertility in some couples previously classified as having unexplained infertility. The recognition of oocyte maturation arrest as a specific medical condition may contribute to the characterization of the yet poorly defined entity currently known as 'oocyte factor'. The cellular and genetic mechanisms causing oocyte maturation arrest should be the subject of further investigation.

Management of male infertility has recently shifted from treatment of the subfertile man towards techniques of assisted reproduction (ART). This study aimed to evaluate the possible role of the ultramorphological status of the spermatozoon with respect to sperm selection in vivo and prediction of ART success. Ultramorphological sperm parameters were assessed retrospectively for 92 males with sufficient sperm density (10(7) spermatozoa ejaculate-1) whose wives conceived following a stepwise discarding of the female genital tract barriers, using intra-uterine insemination (IUI) (n = 26), in vitro fertilization (IVF) (n = 45) or intracytoplasmic sperm injection (ICSI) (n = 21). In parallel, sperm samples of 71 fertile males were examined. Normal ultramorphology of all head and tail subcellular organelles was found to be essential for the ability of spermatozoa to pass the lower female genital tract. The ultramorphological migration threshold for this barrier is apparently higher than that essential for oocyte fertilization. No specific indication associated with passage through the upper genital tract was found. A high prevalence of axonema defects was found to impair the ability of sperm cells to penetrate the oocyte investment. The natural fertility index, based on routine sperm parameters and the ultrastructural status of the spermatozoon's subcellular organelles was confirmed to be beneficial for directing patients to ART. A discriminative score based on axonema integrity was found to contribute additional information for the first choice decision between conventional ART and ICSI (75% prediction ability). Thus it may be helpful in finding the simplest and least expensive procedure with the greatest long-term chance for pregnancy.