Selenium is an antioxidant that helps to protect the eggs and sperm from free radicals. Free radicals can cause chromosomal damage which is known to be a cause of miscarriages and birth defects. Selenium is also necessary for the creation of sperm. In studies, men with low sperm counts have also been found to have low levels of selenium. Selenium even contributes to thyroid health, which is crucial for fertility and pregnancy. Best sources: Liver, snapper, cod, salmon, sardines, shrimp, crimini mushrooms, turkey, Brazil nuts (just one nut contains nearly 100% of the RDA for selenium).