Distribution of Semen Examination Results 2020 - a follow up of data collated for the WHO semen analysis manual 2010

Background: It is now 11 years since publication of the WHO 2010 guidelines for semen assessment values, and it is critical to determine whether they are still valid and/or whether they should be modified. Objectives: To utilise data published since 2010 and combine these with data used in the 2010 assessment to provide an updated and more comprehensive representation of the fertile male. This may be utilised to present an updated distribution of values for use by WHO in 2021. Materials and methods: Two specific analyses were performed namely (1). Analysis 1: Examination of published data following publication of WHO (2010) [termed 2010-2020 data]. (2) Analysis 2: Examination of the data used to help formulate the 2010 distribution of values combined with the data from Analysis (1) [termed WHO 2020]. Results: In total, data from more than 3500 subjects, from 12 countries and 5 continents were analysed. The 5th centiles values for concentration, motility and morphology are: 16 x 106 /ml, 30% progressive motility [42% total motility] and 4% normal forms. Discussion: This study presents substantial additional information to establish more comprehensive and globally applicable reference range intervals for semen parameters for fertile men although they do not represent distinct limits between fertile and subfertile men. There are still data missing from many countries and, some geographical regions are not represented. Moreover, the number of subjects although significant is still relatively low (less than 4000). Conclusion: These distributions of values now include semen analysis providing a more global representation of the fertile male. Increasing the number of subjects provides robust information that is also more geographically representative.