Is it true that tight underwear or pants can decrease your fertility? Yes, it is. The problem with briefs and tight pants is they keep the testicles too close to your body. Testicles hang outside the body because your average body temperature is around 98.6 (98 point 6) degrees. Sperm needs to be kept at 92 to 93 degrees for proper production and storage and is destroyed at temperatures over 102 (a hundred and two). When you wear briefs or tight pants, the testicles are pressed close to the body and the penis, raising the temperature. Wearing boxers, however, allows the testicles to hang freely, away from the body, and maintain cooler temperatures. Since it takes 70 to 80 days for sperm cells to mature, you'll need to wear boxers for about two and a half months. If you're used to wearing briefs, it might take time to adjust to boxers. You can try boxer briefs, extended briefs that give more support than regular boxers can. Another option is briefs with a pouch for the testicles. These don't keep the testicles as cool as boxers, but they do keep them cooler than regular briefs.