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.

Elective single embryo transfer: guidelines for practice British Fertility Society and Association of Clinical Embryologists.

Assisted conception treatment is the single most important cause in the increase in multiple pregnancy and births over the last 25 years. Multiple births are associated with significant peri natal morbidity and mortality. Europe has led the way in reducing multiple births by widespread adoption of an elective single embryo policy, which in Belgium is linked to an increase in state funding.

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.

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.

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.