Sperm quality and its relationship to natural and assisted conception: British Fertility Society guidelines for practice.

Reports on the influence of semen parameters on natural or assisted pregnancy are contradictory, suggesting that the many confounding variables which contribute to outcome have not been taken into account. However, it is possible to derive some consensus for both natural and assisted conception by focussing on studies which use WHO-recommended semen analysis on relatively large populations, applying appropriate statistics and accounting for 'female factors'. The concentration of progressively motile sperm has consistently been shown to be the most predictive factor with regard to outcome. Around 64% of studies suggest that a reasonable chance of success with artificial insemination requires at least 5 × 106 motile sperm and this is supported by the WHO's revised reference range for natural conception. Sperm morphology remains controversial, with a lack of standardisation across centres, the adoption of ever-stricter scoring criteria and changing reference values. Antisperm antibodies do not appear to influence outcome independently of sperm motility and agglutination. Sperm DNA damage appears to be related to sperm quality, embryo development and pregnancy loss, yet there remains no consensus on the best testing procedures, clinical reference values and how patients with an adverse result should be managed. In conclusion, laboratories should continue to focus on reducing the uncertainty and improving the quality of their basic semen analysis.

Risks associated with cryopreservation: a survey of assisted conception units in the UK and Ireland.

A number of recent, high-profile incidents involving loss or damage to cryopreserved material held in IVF units or sperm storage centres have highlighted the need for centres to carefully review their cryostorage practice and take action. Critical disasters involving lost or damaged patient material, although high profile, are still thought to be rare, and there has been concern that we should ensure that any response is proportionate to risk. However, as no regulators, manufacturers or similar professional disciplines have collected information in the long term, our knowledge of the true incidence of such adverse events is extremely poor. Recognizing the need for some solid data, the UK Association of Clinical Embryologists (ACE) conducted a survey on the subject, at its joint meeting with the Association of Irish Clinical Embryologists (ICE) (January, 2006). Questions were asked in relation to the risk of: injury to personnel; and potential loss of and potential damage to stored material. The number of serious and not so serious adverse events/situations relating to both staff and sample safety are discussed in detail. The incidence of problems was certainly higher than we had imagined; the lack of general training and awareness amongst our staff is a serious cause for concern, and appears to leave the industry vulnerable. Moreover, the survey highlighted the need for a coordinated approach to the collection of more detailed information both prospectively and retrospectively. Regulators, manufacturers, allied professional bodies and, more importantly, centres should be encouraged to share both recent and historic data relating to adverse events, in order that accurate risk assessments can be made in future.

Bypassing the effect of zona pellucida changes on embryo formation following cryopreservation of bovine oocytes.

OBJECTIVE: To evaluate the effects of zona pellucida changes following the cryopreservation of bovine oocytes using two different techniques. DESIGN: Prospective randomised study. SETTING: University research facility and IVF research laboratory, NURTURE, University of Nottingham, UK. INTERVENTION: 508 bovine oocytes were collected from abattoir-derived ovaries and cryopreserved by slow freezing using standard straws and a new vitrification method using our self-constructed cryoloops. After thawing, the oocytes were inseminated by ICSI and standard IVF. MAIN OUTCOME MEASURES: Oocyte degeneration and oocyte cleavage. RESULTS: Cleavage rates after IVF in fresh oocytes was higher (49.5%) than the cryopreservation groups (slow freezing: 15.4% and vitrification: 25.8%), whereas after ICSI, the rates were similar (fresh: 17.3%, slow freezing: 9.4%, vitrification: 16.0%). CONCLUSIONS: Zona pellucida changes after oocyte cryopreservation significantly reduce the embryo formation rates after IVF. ICSI bypasses this complication and in selected species it could be an appropriate method of insemination.

Cryopreservation of bovine oocytes: is cryoloop vitrification the future to preserving the female gamete?

The cryoloop is a technique where a thin nylon loop is used to suspend a film of cryoprotectant containing the oocytes and directly immersing them in liquid nitrogen. 508 bovine oocytes were collected, of these 351 were cryopreserved by slow freezing using standard straws or a new vitrification method using our self-constructed cryoloops and the remainder were controls. After thawing, the oocytes were inseminated by ICSI or standard IVF. The cryoloop vitrification method yielded a survival rate of 90.5% and the slow freezing technique a rate of 54.4% (p < 0.0001). When ICSI was performed, cryopreservation by the cryoloop vitrification method resulted in very similar cleavage rate to controls (16.0% vs. 17.3%) but slow freezing produced a slightly lower rate (9.4%). Cleavage rates after IVF in fresh oocytes was higher than the cryopreservation groups (49.5% vs. 15.4% and 25.8%), whereas after ICSI the rates were similar in all groups (17.3% vs. 9.4% and 16%). It is concluded that the new cryoloop vitrification technique followed by ICSI produce good embryo formation results and they could hold the future for effective oocyte cryopreservation.