Table 1.

World Health Organization semen parameter reference values

Semen parameters	4th edition*13	5th edition‡12
Volume of ejaculate (ml)	≥2	≥1.5
Sperm concentration (106/ml)	≥20	≥15
Total sperm count (×106)	≥40	≥39
Motility (%)	≥50 progressive (a + b) ≥25 a only	≥40 total motility ≥28 progressive (a + b)
Morphology by Kruger strict criteria (%)	≥15	≥4
Vitality (% viable)	≥75	≥58
White blood cells (106/ml)	<1	<1

^*Limits of adequacy, determined by consensus.

^†Well-defined reference ranges derived using strict statistical analysis.