World Health Organization reference values for human semen characteristics.

Area of Science:

• Reproductive Medicine
• Andrology
• Epidemiology

Background:

• Semen quality is a key indicator for male fertility, reproductive health, and pregnancy risk.
• Establishing reference intervals for semen parameters is essential for clinical andrology and fertility assessments.

Purpose of the Study:

• To generate reference distributions for semen parameters in a fertile male population.
• To provide data for diagnosing infertility and assessing male fecundity.

Main Methods:

• Analysis of semen samples from over 4500 men across 14 countries.
• Inclusion of men with partners achieving pregnancy within 12 months (time-to-pregnancy < or = 12 months) to define fertile reference groups.
• Generation of distributions for both fertile and general populations.

Main Results:

• Defined lower reference limits (5th centiles) for semen volume (1.5 ml), total sperm number (39 million), sperm concentration (15 million/ml), vitality (58%), progressive motility (32%), total motility (40%), and normal morphology (4.0%).
• Semen quality in the defined fertile reference population was found to be superior to that of the general population and normozoospermic men.

Conclusions:

• The study provides robust reference distributions for semen characteristics of fertile men globally.
• These data serve as a valuable tool for evaluating male semen quality and fertility prospects in clinical settings.