prenatal lethality embryonic lethality MPheno.ontology Note that a term with the former name embryonic lethality exists as MP:0002080. In many species, the terms prenatal lethality and embryonic lethality are used interchangeably. However, this is not technically correct and we have modified this ontology to define the prenatal period to include the embryonic stages distinctly from the fetal stages. The names embryonic lethality and embryonic death have been retained as a narrow synonyms for the prenatal lethality term to aid in searching for those species that may use these terms as synonyms. death of an animal within the embryonic period prior to organogenesis (Mus: prior to E14) embryonic death MP:0008762