Thanks for your question. A lot of people have questions about fertility.
As you know, a varicocele is a dilated vein in your scrotum. Varicoceles are most commonly on the left side of your scrotum. For most people varicoceles don’t cause any issues. However, for some people it can cause pain on the side of the varicocele, affect the size of their testicle, and less commonly affect their fertility. If your varicocele is small and not causing any other symptoms, it probably won’t affect your fertility. If you are concerned you can ask your health care provider. They may do a physical exam, some blood tests, and/or sperm analysis (i.e. tests of your sperm).
A lot of people have questions about how tight underwear and jeans may affect fertility. Some research shows it may affect fertility and some research shows it does not affect fertility. We know sperm production is decreased if the temperature is too hot. This is part of the reason why your testicles are on the outside of your body; in other words, your internal body temperature is too hot. Ultimately many health care providers don’t think that tight clothing will change the temperature of your scrotum enough to make a difference on fertility. So you don’t have to worry about tight clothing affecting your fertility.