title: World Health Organization reference values for human semen characteristics.
abstract: BACKGROUND
  Semen quality is taken as a surrogate measure of male fecundity in clinical andrology, male fertility, reproductive toxicology, epidemiology and pregnancy risk assessments. Reference intervals for values of semen parameters from a fertile population could provide data from which prognosis of fertility or diagnosis of infertility can be extrapolated.
  
  
  METHODS
  Semen samples from over 4500 men in 14 countries on four continents were obtained from retrospective and prospective analyses on fertile men, men of unknown fertility status and men selected as normozoospermic. Men whose partners had a time-to-pregnancy (TTP) of < or =12 months were chosen as individuals to provide reference distributions for semen parameters. Distributions were also generated for a population assumed to represent the general population.
  
  
  RESULTS
  The following one-sided lower reference limits, the fifth centiles (with 95th percent confidence intervals), were generated from men whose partners had TTP < or = 12 months: semen volume, 1.5 ml (1.4-1.7); total sperm number, 39 million per ejaculate (33-46); sperm concentration, 15 million per ml (12-16); vitality, 58% live (55-63); progressive motility, 32% (31-34); total (progressive + non-progressive) motility, 40% (38-42); morphologically normal forms, 4.0% (3.0-4.0). Semen quality of the reference population was superior to that of the men from the general population and normozoospermic men.
  
  
  CONCLUSIONS
  The data represent sound reference distributions of semen characteristics of fertile men in a number of countries. They provide an appropriate tool in conjunction with clinical data to evaluate a patient's semen quality and prospects for fertility.
authors.affiliation: Centre of Reproductive Medicine and Andrology of the University, Domagkstrasse 11, Münster, Germany. tgcooper@gmx.de
authors.forename: Trevor G
authors.initials: TG
authors.lastname: Cooper
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Noonan
authors.forename: Sigrid
authors.initials: S
authors.lastname: von Eckardstein
authors.forename: Jacques
authors.initials: J
authors.lastname: Auger
authors.forename: H W Gordon
authors.initials: HW
authors.lastname: Baker
authors.forename: Hermann M
authors.initials: HM
authors.lastname: Behre
authors.forename: Trine B
authors.initials: TB
authors.lastname: Haugen
authors.forename: Thinus
authors.initials: T
authors.lastname: Kruger
authors.forename: Christina
authors.initials: C
authors.lastname: Wang
authors.forename: Michael T
authors.initials: MT
authors.lastname: Mbizvo
authors.forename: Kirsten M
authors.initials: KM
authors.lastname: Vogelsong
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005220:Fathers / Q000706:statistics & numerical data; D006801:Humans; D007248:Infertility, Male / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012661:Semen / Q000737:chemistry* / Q000166:cytology; D055101:Semen Analysis / Q000379:methods / Q000706:statistics & numerical data*; D014944:World Health Organization; D055815:Young Adult