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				 Volume 15, Issue 2 (March 2013) 15, 169–173; 10.1038/aja.2012.143 
				Trends in global semen parameter values 
				Harry Fisch and Stephen R Braun 
				Departments of Urology and Reproductive Medicine, Weill Cornell Medical College, New York Presbyterian Hospital, New York, NY 10028, USA 
				Correspondence: Dr H Fisch, (harryfisch@aol.com) 
				Received 23 October 2012; Revised 5 November 2012; Accepted 13 November 2012 Advance online publication 7 January 2013 
				
					
						| Abstract | 
					 
					
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						 Allegations for a worldwide decline in semen parameter values have not withstood scientific scrutiny. Methodological flaws in an influential 1992 paper are summarized here, and studies that have been published since 1992 are reviewed. Of the 35 major studies of time trends in semen quality reviewed here, eight (a total of 18 109 men) suggest a decline in semen quality; 21 (112 386 men) show either no change or an increase in semen quality; and six (26 007 men) show ambiguous or conflicting results. The cause (or causes) of the geographical and temporal variations in semen parameter values reported by these diverse studies deserve further investigation. 
						
						
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