Table 3. Studies presenting ambiguous results (total sample size=26 007).

Year	First author	Sample size (N)	Study period	Location	Major findings
1995	Comhaire46	360	NA	Belgium	1. Motility and morphology exhibited ‘highly significant decreases'.
					2. Total sperm count did not decrease.
					3. 40% of donors after 1990 exhibited ‘subnormal' sperm compared with only 5% of group investigated before 1980.
1996	van Waeleghem47	416	NA	Belgium	1. Volume increased slightly.
					2. Mean concentration declined by 12.4 million per ml in study period.
					3. Sperm count was unchanged.
					4. Normal morphology decreased from 39.2% in 1977–1980 to 26.6% in 1990–1995.
1996	de Mouzon48	7714	1989–1995	France	1. No decline in sperm counts when data were analyzed by year of collection.
					2. Sperm counts declined ‘regularly' for men born from 1950 to 1975.
1997	Zheng49	8608	1968–1992	Denmark	1. Semen quantity and quality did not decline with increasing year of birth during the entire period from 1922 to 1972.
					2. From 1950 onward there was a gradual decline in sperm count and normal sperm forms but not in semen volume.
					3. Decline in total sperm count was 1.9 million per ml per year of advancing year of birth.
1999	Ulstein50	5180	1975–1994	Norway	1. Two subgroups of study subjects showed declines in semen parameters.
					2. Subgroup of men with previous children did not show decline in semen parameters.
2010	Mukhopadhyay51	3729	1981–1985–2000–2006	India	1. Mean semen concentration rose from 84×106 per ml in 1980s to 87×106 per ml in 2000s.
					2. Volume declined slightly from mean of 2.97 ml to 2.7 ml.
					3. Motility declined slightly from 60.6% to 58%.

Abbreviation: NA, not applicable.