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

Abstract

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.

DNA fragmentation in brighter sperm predicts male fertility independently from age and semen parameters

“…Semen analysis is routinely used to evaluate the male factor of infertile couples and is considered to be the cornerstone evaluation in male fertility workups. However, whether or not semen analysis predicts natural conception is still controversial (3)(4)(5). The predictive power of standard semen parameters is further complicated by the high technical (intra-and interassay [6,7]) and biologic (intra-individual [8,9]) variability of the measurements of semen parameters.…”

Uncertainty of measurement and clinical value of semen analysis: has standardisation through professional guidelines helped or hindered progress?

“…There is a general agreement that sperm number, motility and velocity are all important for conception, yet this is by no means universal. The evidence in support of other parameters particularly morphology, sperm antibodies or DNA fragmentation is particularly controversial (Larsen et al, 2000;Guzick et al, 2001;Garrett et al, 2003;Cooper et al, 2009;Barratt et al, 2010;Tomlinson et al, 2013). In addition to this general weakness in clinical validation, a number of other factors add weight to and act as evidence of 'uncertainty of measurement' associated with testing including:…”

“…• Variation in practice in relation to treatment decision-making based on sperm quality (Andersen et al, 2008;Tomlinson et al, 2013;Ombelet et al, 2014). A convincing indicator of uncertainty at 'bench level' is the EQA data from UKNEQAS (National External Quality Assurance Scheme) and American Association of Bioanalysts National Proficiency testing (Keel et al, 2000;Tomlinson, 2010).…”

“…This is before any female factors or indeed factors related to the optimisation of treatment success are considered. A review by Tomlinson et al (2013) summarises such 'confounding factors' in a single IVF cycle which contribute to outcome. Although not an exhaustive list, semen variables (concentration, motility, morphology and volume) represented only 13% (4/30) among a list of both clinical (including female factors) and embryological parameters deemed to contribute to a positive outcome, so it is perhaps no wonder that it is difficult to know answers to questions such as: What is the minimum or optimum number of morphologically normal or progressively motile spermatozoa required to result in pregnancy?…”

“…However, it should at least inform the medical team as to: (i) whether a male factor might be responsible for a couple's subfertility, and (ii) help to identify the most appropriate treatment. Evidence suggests that despite the efforts of the World Health Organization and their published guidelines (WHO, 1987;WHO, 1992;WHO, 1999WHO, , 2010 conventional semen analysis remains in some cases poorly standardised, poorly reproducible and according to many authors provides only weak prognostic information (Barratt et al, 2011;Hotaling et al, 2011;De Jonge, 2012;S anchez et al, 2013;Tomlinson et al, 2013). Data from some laboratories suggests strong associations between natural or assisted conception and either sperm number, motility, morphology, sperm antibodies or DNA fragmentation; yet, many others have failed to replicate such findings and few agree on what characteristics are required to achieve a pregnancy (Barratt et al, 1993(Barratt et al, , 2011Weber et al, 2005;Bj€ orndahl, 2011;van den Hoven et al, 2015).…”