RESUMEN
Folates are group B vitamins involved in the one-carbon metabolism. They are required for purine and pyrimidine, and thus DNA synthesis, as well as for the remethylation of homocysteine into methionine which is further metabolized into S-adenosylmethionine, the universal methyl donor for transmethylation of DNA. By this way, folates play a key role in epigenetic regulation of gene expression. Folate deficiency, either by insufficient nutritional uptake or linked to some single nucleotide polymorphism, will lead to an impaired DNA synthesis and repair, a hypomethylation of DNA and other molecules, and homocysteine accumulation. This situation has been associated with several pathologies, such as cardiovascular and neurodegenerative diseases, and pregnancy complications. However, much less is known until now about the impact of one-carbon metabolism on initial events of human reproduction, from gametogenesis to early embryonic development. The present review will deal with these aspects of folate metabolism with respect to male and female fertility.