The quality of semen has declined in the past 20 years, according to studies that looked at falling sperm counts and evidence of reduced motility. In the past, some scientists attributed this decline in sperm quality to environmental factors, such as exposure to toxins, and male smoking during reproductive years. However, not all scientists were on board with this explanation.

New research, based on a 20-year follow-up of one of the world’s largest cohort studies, suggests certain factors in the womb and in early life may affect testicular function later on. These factors include slow fetal growth, exposure to maternal smoking, and poor growth through childhood.

Roger Hart, Professor of Reproductive Medicine at the University of Western Australia and medical director of Fertility Specialists of Western Australia in Perth announced the study results at the July 2013 meeting of the European Society of Human Reproduction and Embryology. Researchers based this recent study on a 20-year follow-up of the Western Australian Pregnancy (Raine) Cohort, the most successful and extensive longitudinal study of its kind. The Raine Cohort began in 1989 – 1991, enrolling 2900 mothers during pregnancy. The babies had regular assessments, including fetal growth measurements, from birth. Part of the recent 20-year follow-up study included 423 men between the ages of 20 and 22 years; these men consented to measurements of testicular volume, analysis of semen quality and hormone production. Researchers also measured body composition for fat distribution.

Test Results
About one in six of these male participants had sperm parameters below normal as defined by the World Health Organization (WHO). More than a quarter of participants had sperm that did not fit WHO’s acceptable criteria for appearance.

  • 14.8% were below the threshold of 1.5 ml seminal volume
  • 18.9% below the threshold of 39 million total sperm
  • 17.5% below the threshold of 15 million sperms/ml sperm count
  • 14.4% below the threshold of 32% motility

Researchers correlated male participant results with fetal growth assessments gathered during the mothers’ pregnancy and found that fetuses that grow slowly have a significantly higher risk for low sperm counts as mature males. Exposure to maternal smoking, as 18 percent of study subjects were, is also associated with low sperm count later in life.

Any male concerned about low sperm count should contact his doctor or a reproduction specialist for a sperm assessment and fertility counseling.


  • European Society of Human Reproduction and Embryol. "Potential Link Between Impaired Fetal Growth, Exposure To Maternal Smoking And Lower Measures Of Sperm Quality." Medical News Today. MediLexicon, Intl., 9 Jul. 2013. Web. 23 Sep. 2013.
  • Raine Study
  • Cooper, Trevor G., et al. "World Health Organization reference values for human semen characteristics." World Health Organization. 2009. Web. 23 Sept 2013.