Objective: the objective of the present work is to review the epidemiology, the clinical classification, the diagnosis and the treatment of the pre gestational and gestational diabetes. Materials and methods: with the key words: diabetes, gestational diabetes, pregestational diabetes,diabetesandpregnancywordsinformation we looked for data bases of Pubmed/Medline, Cochrane, SciELO, like in article references of magazine and texts mainly of last the five years. The result of this search threw 79 references from which they were taken 35 more relevant, vtaking vmainly meta analysis, review articles, state of the art, double-blind, randomized studies and practice guideline. We used the following. Results: good control of glycemia during pregnancy avoids or reduces maternal and foetal complications. It is known that women have suffered diabetes prior to their becoming pregnant in 0.2%-0.3% of all pregnancies and that gestational diabetes complicates 1%-14% of all pregnancies. WHO criteria require > 140 mg/dl glycemia at 2 hours post-test, 75 g oral glucose being necessary for diagnosing gestational diabetes. Diagnosis can also be made from two glycemia readings of > 105 mg/dl on an empty stomach or one > 126 mg/dl glycemia reading on an empty stomach or a > 200 mg/dl glycemia reading regardless of the time of day and time of the last meal. Conclusion: a better control of the numbers of glucosa during the pregnancy is associate to a greater fetal well-being.