Both of these are associated with poor sperm quality in men and lower conception rates in women. Smoking and alcohol use during pregnancy also negatively affect the unborn child and may result in low birth weight babies. Anti-cancer drugs can cause ovarian and testicular failure temporarily or permanently. Additionally, many drugs can cause miscarriage or fetal defect once pregnancy has begun. Avoiding all medications while attempting to conceive and during pregnancy is best whenever possible.
Any surgery involving the reproductive structures can lead to infertility.
Talk to your doctor in detail about the implications of the surgery on future reproductive functioning beforehand. Of course, surgical sterilization will usually cause infertility and should be considered permanent. High doses can cause miscarriage or fetal defect in pregnant women. There's no evidence that endurance training leads to male infertility. Men's briefs and tight pants have been thought to have the same effect on sperm as heat exposure and hot baths, however there is no scientific evidence for this hypothesis.