Table 2.

Changes in Reference Values from the second to the sixth edition of the WHO Laboratory Manual for the Examination and Processing of Human Semen

Edition	Nomenclature	Semen volume (ml)	Sperm concentration (106/ml)/Total no. (106/ejaculate)	Total /progressive sperm motility (%)	Normal forms (%)	Reference
2nd	Normal values	≥2	≥20/≥40	≥50/≥25	≥50	Modified from (3, 4, 5), data from 1,000 men with known fertility (female partner currently pregnant) and 1,000 men in infertile marriage
3rd	Normal values	≥2	≥20/≥40	≥50/≥25	≥30	Same as 2nd Edition Empirical value used for normal sperm forms
4th	Reference values	≥2	≥20/≥40	≥50/≥25	∗	Same as 3rd Edition. ∗ Normal forms—population-based studies of normal forms in progress, data from assisted reproductive technology suggest <15 normal forms may be associated with decreased in vitro fertilization rate
5th	Reference values of fertile men (5th centile lower reference limits)	1.5	15/39	40/32	4	Population-based studies of approximately 1,900 fertile men (defined as men whose partner conceived within 12 months after stopping contraception) (23). Morphology using “strict” criteria (8, 11)
6th	Distribution of semen variables from fertile men (5th centile)	1.4	16/39	42/30	4	Population-based studies of approximately 3,500 fertile men (defined as men whose partner had a natural conception with a confirmed time to pregnancy of ≤12 months) (41). Morphology using “strict” criteria (8, 11)