There is no scientific evidence that links exercise with a miscarriage. Although certain kinds of exercise will need to be stopped as the pregnancy progresses. For example, marathon running and mountain biking are not exactly suitable for a woman who is 7 months pregnant. A doctor should be consulted on what kinds of exercise are okay and what should be stopped for the duration of the pregnancy.

Sexually transmitted infections — such as chlamydia and gonorrhea — are a leading cause of infertility for both men and women.

Sexually transmitted infections such as chlamydia and gonorrhea can cause fallopian tube damage.

Antibiotic treatment may cure an infection of the reproductive tract, but doesn't always restore fertility. Your doctor may recommend hormone replacement or medication in cases where infertility is caused by high or low levels of certain hormones or problems with the way the body uses hormones. A varicocele can often be surgically corrected or an obstructed vas deferens repaired.

Fibroids can contribute to infertility and are found in 5% to 10% of infertile women.

Only barrier methods (male condoms and internal condoms) prevent pregnancy and STIs. The rest only protect against pregnancy but not from infections.