Wearing tight underwear may damage sperm quality! Nearly 27,000 people studied the relationship to reveal whether it would really affect pregnancy?

Does wearing too tight men's underwear really affect fertility? A new study involving nearly 27,000 men found that those who wore tight-fitting underwear had poorer semen quality on multiple indicators and a higher proportion of sperm DNA fragmentation. However, research cannot prove that the style of underwear causes infertility, nor can it confirm that wearing loose boxer briefs can increase the chance of pregnancy.

According to a report by the New York Post on the 8th, this study was conducted by a team from the University of Science and Technology of China and was published in the Asian Journal of Andrology on October 27. The study included 26,836 men undergoing fertility assessment, of which 21,221 were accustomed to wearing loose underwear and 5,615 were accustomed to wearing tight-fitting styles, and the semen test results of the two groups were compared.

After adjusting for other health factors, the study found that the tight-fitting underwear group had lower semen volume, worse sperm motility and normal morphology ratio, and a higher sperm DNA fragmentation index, and the odds of winning were about 2.08 times that of the loose-fitting underwear group. The study also found that the tight underwear group also had higher rates of erectile dysfunction and premature ejaculation. However, this is still a preliminary observation and cannot be used to conclude that wearing tight underwear will cause sexual dysfunction.

The rising temperature of the scrotum may affect sperm production, but there is no evidence that it affects pregnancy.

The research team speculates that tight underwear may increase scrotal temperature, thereby affecting sperm production. However, this study adopted a cross-sectional design, and the underwear wearing habits were reported by the subjects themselves, so it is impossible to confirm the cause and effect; and the study subjects were originally men seeking fertility evaluation, so the results cannot be directly applied to all men.

This isn't the first study of underwear and fertility, either. A 2018 Harvard study published in "Human Reproduction" analyzed the data of 656 men undergoing infertility evaluation and found that those who habitually wore boxer briefs had higher sperm concentration and total count, but it also could not prove that the style of underwear was the cause of the difference.

A literature review published in Translational Andrology and Urology in May 2026 pointed out that the results of past studies on semen quality are inconsistent, and the existing data does not show a clear correlation between underwear style and actual pregnancy outcomes. In other words, loose-fitting underwear may help reduce scrotal heating, but there is currently insufficient evidence to prove that simply changing underwear can improve fertility.