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Updated: Jun 27, 2026

Sperm Collection of Differential Quality Using Density Gradient Centrifugation
Published on: November 29, 2018
Declining sperm quality in New Zealand over 20 years
Rebecca Shine1, John Peek, Mary Birdsall
1University of Auckland School of Medicine, Auckland, New Zealand.
Aim:
To investigate whether semen quality has changed in New Zealand over the last 20 years.
Method:
A retrospective study from 1987 to 2007. The sperm concentration, volume of seminal fluid, and the percentage of motile sperm were analysed from the first semen sample of 975 men presenting as sperm donors in Auckland and Wellington.
Results:
Linear regression showed that the mean concentration of sperm decreased from 110 x 10(6) per millilitre in 1987 to 50 x 10(6) per millilitre in 2007 (p<0.001); an average reduction of 2.5% annually. The volume of semen also fell significantly from 3.7 ml to 3.3 ml (p<0.001). There was no concomitant change in the duration of abstinence.
Conclusion:
The decline in semen volume and sperm concentration in men presenting as sperm donors may indicate a reduction in the semen quality of New Zealand men over the past 20 years.
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