
Previous meta‐analyses concluded that there is a decline in sperm parameters over time. This conclusion might be incorrect due to inherent biases or focusing only on a single parameter – sperm concentration. To study trends in sperm parameters over the past twenty years using data from the trials that defined the reference ranges of the World Health Organization manual. Retrospective evaluation of the data used to define the World Health Organization reference ranges. The data from 11 studies, including 3589 participants between 1996–2016, were divided into three period groups based on the decade of study...
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