Table 1.

Cutoff reference values for semen characteristics as published in the 1999 and 2010 World Health Organization (WHO) manuals for laboratory examination of human semen. The reference limits in the 2010 WHO manual were set as the values within the fifth centile distribution of semen parameters of approximately 2000 men whose partners had a time-to-pregnancy of 12 months or less. The corresponding 50th and 95th centiles are also provided (adapted from Cooper et al [23] and Esteves et al. [22])

Semen parameters	WHO 1999a	WHO 2010b
		5th centile	50th centile	95th centile
Volume (mL)	≥2	1.5	3.7	6.8
Sperm count (106/mL)	≥20	15	73.0	213.0
Total sperm count (106)	≥40	39	255.0	802.0
Total motility (% motile)	≥50	40	61	78
Progressive motility	≥25 %c	32 %d	55	72
Vitality (% alive)	≥75	58	15	44
Morphology (% normal forms)	(14)e	4f	79	91

^aReference values based on the clinical experience of investigators who have studied populations of healthy fertile men of unknown time-to-pregnancy

^bReference limits obtained from the 5th centile values

^cGrade a = rapid progressive motility (>25 μm/s)

^dProgressive motility irrespective of grades

^eValue not defined, but strict criterion is suggested

^fStrict (Tygerberg) criterion