Palate formation occurs between the fifth and eleventh week of intrauterine life as a result of the union of the primary and secondary palate. On the other hand, the formation of the upper lip occurs between the fifth and sixth week of development, and is configured in its middle part by the fusion of the medial and lateral nasal processes, at the expense of the maxillary processes. The prevalence of cleft lips and / or cleft palate varies according to the different ethnic groups, with figures ranging from 0.7 to 1.1 ca- ses per 1000 live births. The aim of this work was to carry out a literature review on epidemiological aspects, molecular and environmental genetic mechanisms that influence the occurrence of cleft lip, cleft palate and its embriology. The literature search was carried out in the databases PUBMED, SCOPUS, SPRINGER, SCIENCEDIRECT using the English terms "cleft lip and palate", "cleft lip", "cleft palate" and "embryology". Inclusion criteria included studies carried out in humans and animals, published between 2015 and 2021. The search yielded a total of 407 works, of which after a filter by title and abstract, a total of 38 articles remained, in which a text analysis was carried out complete to finally select 26 articles that cover genetic-molecular, environmental, epidemiological and syndromic topics. In addition, 6 documents associated with textbooks and scientific articles were incorporated by manual search, without considering the inclusion criterion of time. This review describes the strong association between oral fissures and mutations of genes Msx1, sonic hedgehog, bone morphogenetic proteins and fibroblast growth factor during migration of neural crest cells and palate shaping and formation. Lack of folic acid during palae development dar and the presence of hypoxia due to exposure to smoke, are the environmental factors most frequently observed in orofacial malformations.
KEY WORDS: Cleft lip; Ceft palate; Embriology.