Penis Size Study: Male Fertility Linked to Size of Genitals

Penis size has been linked to infertility in a study. 

Scientists at the University of Utah, Salt Lake City, set out to answer whether penis size affects a man's fertility, and found that men with organs measuring 12.5 centimeters on average struggled to conceive compared with those who measured 13.4 centimeters. This is believed to be the first study to make the association between fertility and penis length. 

According to the U.S. Department of Health, infertility is defined as when a couple cannot conceive after one year of unprotected intercourse. The causes of infertility can be varied and accumulative, but testicular problems are the most common cause in men followed by hormone problems and blockages. In half of cases, no definitive cause can be pinpointed. 

To conduct the study, researchers analyzed data on 815 men aged between 18 and 59 who had attended a health clinic between 2014 and 2017.

The participants underwent a test known as the Stretched Penile Length (SPL), which is used to approximate the length of the organ when it is erect. A man’s age, weight and race were also taken into account by the team.

sperm-stock The size of a man's penis could affect their fertility, a study has suggested. Getty Images

Read more: Men could be predisposed to erectile dysfunction via genetics 

Of the total volunteers, 219 men visited the facility to get help for fertility problems, while the remainder sought to solve conditions such as erectile dysfunction and testicular pain.

The authors wrote that the apparent difference in fertility may lie in genetic, congenital factors such as testicular dysgenesis syndrome—a condition that can affect the ability to reproduce, or hormone imbalances.

The study was presented as a poster at the American Society for Reproductive Medicine conference in Colorado, and has therefore not been peer reviewed and published in a medical journal. 

Lead author of the study, Dr. Austen Slade from the University of Utah, Salt Lake City, urged men with smaller than average genitalia not to be concerned about their fertility and explained that the study "raises more questions that it answers."

There was a clear statistical correlation between men with a smaller than average penis size and infertility, he said. However, he stressed: “There are lots of men with below average penile lengths who have normal fertility, and many with above average length who have faced infertility."

Dr. Ryan P. Terlecki, an expert in men’s health and associate professor of urology, obstetrics and gynecology at Wake Forest Baptist Health, North Carolina, told Newsweek that although the paper is currently only in abstract form, the results are “interesting.”

The study raises several questions, such as how infertility was defined and the hormone levels in each group. 

"It would be interesting to know if the men with a shorter penile length had lower testosterone,” he said. 

Dr. Sheena Lewis, fertility expert and at the Centre for Public Health at Queen's University Belfast, U.K. told Newsweek: "In a larger population we might find that many fertile men have shorter SPL than infertile men."

Important information is also missing from the research, Lewis argues: "Were the female partners infertile? If so this would confound the findings. The men in the ‘fertile’ group were attending clinics for other reproductive problems so that was a further confounding factor. Had all those men fathered children recently? If not, they were not an ideal control group."

Terlecki continued: "If this data holds up when a full paper is scrutinized, and if other centers confirm these findings, it may suggest a value in penile length assessments for men presenting with infertility." 

The study follows a paper published in the Proceedings of the National Academy of Sciences that suggested genetics could play a role in erectile dysfunction. 

Scientists found that some men with the condition carried a genetic variant that could inhibit the production of a protein linked to the ability to get an erection. 

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